Skyscraper

For other uses, see Skyscraper (disambiguation).

A skyscraper is a tall, continuously habitable building of many stories, often designed for office and commercial use. There is no official definition or height above which a building may be classified as a skyscraper. One common feature is that skyscrapers tend to make use of a steel framework structure from which walls are suspended, rather than having load-bearing walls as seen in conventional buildings.

As there is no official definition of what constitutes a skyscraper, a relatively small building may be considered one if it protrudes well above its built environment and changes the overall skyline. The maximum height of structures has progressed historically with building methods and technologies. 'Supertall' has arisen as a contemporary expression for exceptionally tall buildings, although again there is no formal definition.

Definition

The word "skyscraper" originally was a nautical term referring to a small triangular sail set above the skysail on a sailing ship. The term was first applied to buildings of steel framed construction of at least 10 storeys in the late 19th century, a result of public amazement at the tall buildings being built in major cities like Chicago, New York City, Detroit, and St. Louis.^[1] The first steel frame skyscraper was the Home Insurance Building (originally 10 storeys with a height of 42 m or 138 ft) in Chicago, Illinois in 1885. Some point to New York's seven-floor Equitable Life Assurance Building, built in 1870, as an early skyscraper for its innovative use of a kind of skeletal frame, but such designation depends largely on what factors are chosen. Even the scholars making the argument find it to be purely academic.^[2]

The structural definition of the word skyscraper was refined later by architectural historians, based on engineering developments of the 1880s that had enabled construction of tall multi-storey buildings. This definition was based on the steel skeleton—-as opposed to constructions of load-bearing masonry, which passed their practical limit in 1891 with Chicago's Monadnock Building. The steel frame developed in stages of increasing self-sufficiency, with several buildings in Chicago and New York advancing the technology that allowed the steel frame to carry a building on its own. Today, however, many of the tallest skyscrapers are built almost entirely with reinforced concrete.^[3]

Skyscraper and supertall

The Emporis Standards Committee defines a high-rise building as "a multi-storey structure between 35–100 metres tall, or a building of unknown height from 12–39 floors"^[4] and a skyscraper as "a multi-storey building whose architectural height is at least 100 metres."^[5] Some structural engineers define a highrise as any vertical construction for which wind is a more significant load factor than earthquake or weight. Note that this criterion fits not only high-rises but some other tall structures, such as towers.

The word skyscraper often carries a connotation of pride and achievement. The skyscraper, in name and social function, is a modern expression of the age-old symbol of the world center or axis mundi: a pillar that connects earth to heaven and the four compass directions to one another.^[6]

A loose convention of some in the United States and Europe draws the lower limit of a skyscraper at 150 metres (~500 ft).^[7]

History

The Two Towers of Bologna in the 12th century reached 97.2 m in height.

The 16th-century city of Shibam consisted entirely of over 500 high-rise tower houses.

Before the 19th century

Modern skyscrapers are built with materials such as steel, glass, reinforced concrete and granite, and routinely utilize mechanical equipment such as water pumps and elevators. Until the 19th century, buildings of over six stories were rare, as having great numbers of stairs to climb was impractical for inhabitants, and water pressure was usually insufficient to supply running water above 50 m (164 ft).

The tallest building in ancient times was the Great Pyramid of Giza in ancient Egypt, which was 146 metres (479 ft) tall and was built in the 26th century BC. Its height was not surpassed for thousands of years, possibly until the 14th century AD with the construction of Lincoln Cathedral (though its height is disputed),^[8] which in turn was not surpassed in height until the Washington Monument in 1884. However, being uninhabited buildings, none of these buildings actually complies with the definition of a skyscraper.

High-rise apartment buildings already flourished in classical antiquity: ancient Roman insulae in Rome and other imperial cities reached up to 10 and more stories.^[9] Several emperors, beginning with Augustus (r. 30 BC-14 AD), attempted to establish limits of 20–25 m for multi-storey buildings, but met with only limited success.^[10][11] The lower floors were typically occupied by either shops or wealthy families, while the upper stories were rented out to the lower classes.^[9] Surviving Oxyrhynchus Papyri indicate that seven-storey buildings even existed in provincial towns, such as in 3rd century AD Hermopolis in Roman Egypt.^[12]

The skylines of many important medieval cities had large numbers of high-rise urban towers. Wealthy families built these towers for defensive purposes and as status symbols. The residential Towers of Bologna in the 12th century, for example, numbered between 80 to 100 at a time, the largest of which (known as the "Two Towers") rise to 97.2 metres (319 ft). In Florence, a law of 1251 decreed that all urban buildings should be reduced to a height of less than 26 m, the regulation immediately put into effect.^[13] Even medium-sized towns at the time such as San Gimignano are known to have featured 72 towers up to 51 m height.^[13]

The medieval Egyptian city of Fustat housed many high-rise residential buildings, which Al-Muqaddasi in the 10th century described as resembling minarets. Nasir Khusraw in the early 11th century described some of them rising up to 14 stories, with roof gardens on the top floor complete with ox-drawn water wheels for irrigating them.^[14] Cairo in the 16th century had high-rise apartment buildings where the two lower floors were for commercial and storage purposes and the multiple stories above them were rented out to tenants.^[15] An early example of a city consisting entirely of high-rise housing is the 16th-century city of Shibam in Yemen. Shibam was made up of over 500 tower houses,^[16] each one rising 5 to 11 storeys high,^[17] with each floor being an apartment occupied by a single family. The city was built in this way in order to protect it from Bedouin attacks.^[16] Shibam still has the tallest mudbrick buildings in the world, with many of them over 30 m (98 ft) high.^[18]

An early modern example of high-rise housing was in 17th-century Edinburgh, Scotland, where a defensive city wall defined the boundaries of the city. Due to the restricted land area available for development, the houses increased in height instead. Buildings of 11 stories were common, and there are records of buildings as high as 14 stories. Many of the stone-built structures can still be seen today in the old town of Edinburgh. The oldest iron framed building in the world, although only partially iron framed, is The Flaxmill (also locally known as the "Maltings"), in Shrewsbury, England. Built in 1797, it is seen as the "grandfather of skyscrapers”, since its fireproof combination of cast iron columns and cast iron beams developed into the modern steel frame that made modern skyscrapers possible. Unfortunately, it lies derelict and needs much investment to keep it standing.

Oriel Chambers, Liverpool. The world's first glass curtain walled building. The stone mullions are decorative.

The Wainwright Building, a 10-story red brick office building in St. Louis, Missouri, built in 1891

Built in 1931, The Empire State Building in New York City is one of the oldest, yet tallest skyscrapers.

Early skyscrapers

An early development was Oriel Chambers in Liverpool. Designed by local architect Peter Ellis in 1864, the building was the world's first iron-framed, glass curtain-walled office building. It was only 5 floors high.^[19][20][21] Further developments led to the world's first skyscraper, the ten-storey Home Insurance Building in Chicago, built in 1884–1885. While its height is not considered very impressive today, it was at that time. The architect, Major William Le Baron Jenney, created a load-bearing structural frame. In this building, a steel frame supported the entire weight of the walls, instead of load-bearing walls carrying the weight of the building. This development led to the "Chicago skeleton" form of construction.

Louis Sullivan's Wainwright Building in St. Louis, Missouri, 1891, was the first steel-framed building with soaring vertical bands to emphasize the height of the building and is therefore considered by some to be the first true skyscraper.

Most early skyscrapers emerged in the land-strapped areas of Chicago, London, and New York toward the end of the 19th century. A land boom in Melbourne, Australia between 1888–1891 spurred the creation of a significant number of early skyscrapers, though none of these were steel reinforced and few remain today. Height limits and fire restrictions were later introduced. London builders soon found building heights limited due to a complaint from Queen Victoria, rules that continued to exist with few exceptions until the 1950s. Concerns about aesthetics and fire safety had likewise hampered the development of skyscrapers across continental Europe for the first half of the twentieth century (with the notable exceptions of the 1898 Witte Huis (White House) in Rotterdam; the Royal Liver Building in Liverpool, completed in 1911 and 90 m (300 ft) high;^[22] and the 17-storey Kungstornen (Kings' Towers) in Stockholm, Sweden, which were built 1924–25^[23], the 15-storey Edificio Telefónica in Madrid, Spain, built in 1929; the 26-storey Boerentoren in Antwerp, Belgium, built in 1932; and the 31-storey Torre Piacentini in Genoa, Italy, built in 1940). After an early competition between Chicago and New York City for the world's tallest building, New York took the lead by 1895 with the completion of the American Surety Building, leaving New York with the title of tallest building for many years. New York City developers competed among themselves, with successively taller buildings claiming the title of "world's tallest" in the 1920s and early 1930s, culminating with the completion of the Chrysler Building in 1930 and the Empire State Building in 1931, the world's tallest building for forty years. The first completed World Trade Center tower became the world's tallest building in 1972. However, it was soon overtaken by the Sears Tower (now Willis Tower) in Chicago within two years. The Sears Tower stood as the world's tallest building for 24 years, from 1974 until 1998, until it was edged out by Petronas Twin Towers in Kuala Lumpur, which held the title for six years.

Modern skyscrapers

From the 1930s onwards, skyscrapers also began to appear in Latin America (São Paulo, Santiago, Caracas, Bogotá, Mexico City) and in Asia (Tokyo, Shanghai, Hong Kong, Manila, Singapore, Mumbai, Seoul, Kuala Lumpur, Taipei, Bangkok). Immediately after World War II, the Soviet Union planned eight massive skyscrapers dubbed "Stalin Towers" for Moscow; seven of these were eventually built. The rest of Europe also slowly began to permit skyscrapers, starting with Madrid, during the 1950s. Finally, skyscrapers also began to be constructed in cities of Africa, the Middle East and Oceania (mainly Australia) from the late 1950s.

In the early 1960s structural engineer Fazlur Khan realized that the rigid steel frame structure that had "dominated tall building design and construction so long was not the only system fitting for tall buildings", marking "the beginning of a new era of skyscraper revolution in terms of multiple structural systems."^[24] His central innovation in skyscraper design and construction was the idea of the "tube" structural system, including the "framed tube", "trussed tube", and "bundled tube".^[25] These systems allowed far greater economic efficiency,^[26] and also allowed efficient skyscrapers to take on various shapes, no longer needing to be box-shaped.^[27] Over the next fifteen years, many towers were built by Khan and the "Second Chicago School",^[28] including the massive 442-meter (1,451-foot) Willis Tower.^[29] Since 2000, Cities like Chicago ^[30], Shanghai ^[31], Dubai, New York, and Toronto have experienced a huge surge in skyscraper construction. Chicago, Hong Kong, and New York City, otherwise known as "the big three," are recognized in architectural circles as having especially compelling skylines. A landmark skyscraper can inspire a boom of new high-rise projects in its city, as Taipei 101 has done in Taipei since its opening in 2004. In 2010, The Bank of America Tower at One Bryant Park became the world's first commercial LEED Platinum skyscraper.

History of tallest skyscrapers

Burj Khalifa in Dubai is the tallest building in the world at 828 m (2,717 ft).

Main article: History of the tallest buildings in the world

At the beginning of the 20th century, New York City was a center for the Beaux-Arts architectural movement, attracting the talents of such great architects as Stanford White and Carrere and Hastings. As better construction and engineering technology became available as the century progressed, New York and Chicago became the focal point of the competition for the tallest building in the world. Each city's striking skyline has been composed of numerous and varied skyscrapers, many of which are icons of 20th century architecture:

• The Flatiron Building, designed by Daniel Hudson Burnham and standing 285 ft (87 m) high, was one of the tallest buildings in the city upon its completion in 1902, made possible by its steel skeleton. It was one of the first buildings designed with a steel framework, and to achieve this height with other construction methods of that time would have been very difficult. (The 1889 Tower Building, designed by Bradford Gilbert and considered by some to be New York's first skyscraper, may have been the first building to use a skeletal steel frame.)^[32] Subsequent buildings such as the Singer Building, the Metropolitan Life Tower were higher still.
• The Woolworth Building, a neo-Gothic "Cathedral of Commerce" overlooking City Hall, was designed by Cass Gilbert. At 792 feet (241 m), it became the world's tallest building upon its completion in 1913, an honor it retained until 1930, when it was overtaken by 40 Wall Street.
• That same year, the Chrysler Building took the lead as the tallest building in the world, scraping the sky at 1,046 feet (319 m).^[33] Designed by William Van Alen, an Art Deco style masterpiece with an exterior crafted of brick,^[34] the Chrysler Building continues to be a favorite of New Yorkers to this day.^[35]
• The Empire State Building, the first building to have more than 100 floors (it has 102), was completed the following year. It was designed by Shreve, Lamb and Harmon in the contemporary Art Deco style. The tower takes its name from the nickname of New York State. Upon its completion in 1931 at 1,250 feet (381 m), it took the top spot as tallest building, and towered above all other buildings until 1972. The antenna mast added in 1951 brought pinnacle height to 1,472 feet (449 m), lowered in 1984 to 1,454 feet (443 m).^[36]
• The World Trade Center officially reached full height in 1972, was completed in 1973, and consisted of two tall towers and several smaller buildings. For a short time, the first of the two towers was the world's tallest building. Upon completion, the towers stood for 28 years, until the September 11 attacks destroyed the buildings in 2001. Various governmental entities, financial firms, and law firms called the towers home.
• The Willis Tower (formerly Sears Tower) was completed in 1974, one year after the World Trade Center, and surpassed it as the world's tallest building. It was the first building to employ the "bundled tube" structural system, designed by Fazlur Khan.^[27] The building was not surpassed in height until the Petronas Towers were constructed in 1998, but remained the tallest in some categories until Burj Khalifa surpassed it in all categories in 2010. It is currently the tallest building in the United States.

Momentum in setting records passed from the United States to other nations with the opening of the Petronas Twin Towers in Kuala Lumpur, Malaysia, in 1998. The record for world's tallest building remained in Asia with the opening of Taipei 101 in Taipei, Taiwan, in 2004. A number of architectural records, including those of the world's tallest building and tallest free-standing structure, moved to the Middle East with the opening of the Burj Khalifa in Dubai, United Arab Emirates.

This geographical transition is accompanied by a change in approach to skyscraper design. For much of the twentieth century large buildings took the form of simple geometrical shapes. This reflected the "international style" or modernist philosophy shaped by Bauhaus architects early in the century. The last of these, the Willis Tower and World Trade Center towers in New York, erected in the 1970s, reflect the philosophy. Tastes shifted in the decade which followed, and new skyscrapers began to exhibit postmodernist influences. This approach to design avails itself of historical elements, often adapted and re-interpreted, in creating technologically modern structures. The Petronas Twin Towers recall Asian pagoda architecture and Islamic geometric principles. Taipei 101 likewise reflects the pagoda tradition as it incorporates ancient motifs such as the ruyi symbol. The Burj Khalifa draws inspiration from traditional Islamic art. Architects in recent years have sought to create structures that would not appear equally at home if set in any part of the world, but that reflect the culture thriving in the spot where they stand.

For current rankings of skyscrapers by height, see List of tallest buildings in the world.

The following list measures height of the roof. The more common gauge is the highest architectural detail; such ranking would have included Petronas Towers, built in 1998. See List of tallest buildings in the world for details.

Built	Building	City	Country	Roof		Floors	Pinnacle		Current status
1870	Equitable Life Building	New York City	United States	142 ft	43 m	8			Destroyed by fire in 1912
1889	Auditorium Building	Chicago	United States	269 ft	82 m	17	349 ft	106 m	Standing
1890	New York World Building	New York City	United States	309 ft	94 m	20	349 ft	106 m	Demolished in 1955
1894	Manhattan Life Insurance Building	New York City	United States	348 ft	106 m	18			Demolished in 1930
1895	Milwaukee City Hall	Milwaukee	United States	353 ft	108 m	15			Standing
1899	Park Row Building	New York City	United States	391 ft	119 m	30			Standing
1901	Philadelphia City Hall	Philadelphia	United States	511 ft	155.8 m	9	548 ft	167 m	Standing
1908	Singer Building	New York City	United States	612 ft	187 m	47			Demolished in 1968
1909	Met Life Tower	New York City	United States	700 ft	213 m	50			Standing
1913	Woolworth Building	New York City	United States	792 ft	241 m	57			Standing
1930	40 Wall Street	New York City	United States			70	927 ft	283 m	Standing
1930	Chrysler Building	New York City	United States	927 ft	282.9 m	77	1,046 ft	319 m	Standing
1931	Empire State Building	New York City	United States	1,250 ft	381 m	102	1,454 ft	443 m	Standing
1972	World Trade Center (North tower)	New York City	United States	1,368 ft	417 m	110	1,727 ft	526.3 m	Destroyed in 2001
1974	Willis Tower (formerly Sears Tower)	Chicago	United States	1,450 ft	442 m	108	1,729 ft	527 m	Standing
2004	Taipei 101	Taipei	Taiwan	1,474 ft	449 m	101	1,671 ft	509 m	Standing
2010	Burj Khalifa	Dubai	United Arab Emirates	2,717 ft	828 m	160	2,717 ft	828 m	Standing

Source: emporis.com

Taipei 101, formerly the world's tallest skyscraper, was the first to exceed the half-kilometer mark.   The iconic World Trade Center twin towers were destroyed in 2001.   The Willis Tower in Chicago was the world's tallest building from 1974 to 1998, and remains the tallest in the Western Hemisphere.   The Petronas Twin Towers.   Tower 2 of the International Finance Centre in Hong Kong is one of the 20 tallest buildings in the world.   The City of Capitals in Moscow is the tallest completed skyscraper in Europe.

Today

Today, skyscrapers are an increasingly common sight where land is expensive, as in the centres of big cities, because they provide such a high ratio of rentable floor space per unit area of land. They are built not just for economy of space; like temples and palaces of the past, skyscrapers are considered symbols of a city's economic power. Not only do they define the skyline, they help to define the city's identity.

Supertall towers

At the time Taipei 101 broke the half-kilometer mark in height, it was already technically possible to build structures towering over a kilometer above the ground. Proposals for such structures have been put forward, including the Mile-High Tower to be built in Jeddah, Saudi Arabia^[37][38] and Burj Mubarak Al Kabir in Kuwait. Kilometer-plus structures present architectural challenges that may eventually place them in a new architectural category.^[39]

Future notable skyscrapers

The following skyscrapers, all contenders for being among the tallest in their city or region, are under construction and due to be completed in the next few years:

• Construction of the 133-floor, 640 m tall Digital Media City Landmark Building in Digital Media City, Seoul, South Korea, started in 2009, which will be the second-tallest building in the world when it is completed in 2015, housing the world's tallest observatory and hotels. Being constructed at the fastest speed among major skyscraper projects by South Korea's Samsung C&T (who also built Burj Khalifa), the supertall is the first skyscraper to contain an entire city inside a building, including the world's largest aquarium, a luxury department store, shopping malls, clinic center, high-tech offices, first-class apartments, six to eight-star hotels, a concert restaurant, a broadcasting studio and an art center.
• Construction of the Shanghai Tower started on 29 November 2008.^[40] The tower will be 632 m (2,073 ft) high and have 127 floors.^[41][42] The building will feature a glass curtain wall and nine indoor gardens when it is completed in 2014.^[43][44]
• Construction of the 151-floor, 610 m tall 151 Incheon Tower in Songdo International City, Incheon, South Korea, started in 2008, which will be the tallest twin towers in the world when it is completed in 2014.
• The Abraj Al-Bait Towers, also known as the "Mecca Royal Clock Hotel Tower" is a complex under construction in Mecca, Saudi Arabia by the Saudi Binladin Group. The complex consists of seven towers, and the tallest tower (Hotel Tower) will have a height of 601 m (1,972 ft). Upon completion in 2011, the structure will have the largest floor area of any structure in the world, at 1,500,000 square metres (16,137,600 sq ft).
• Construction of the 110-floor, 510 m tall Busan Lotte World, Busan, South Korea, started in 2009. It is due for completion in 2016.
• One World Trade Center is currently under construction in New York City and will be the tallest tower in the redevelopment of the site of the former World Trade Center.^[45] Its pinnacle will reach a height of 541.4 m (1,776 ft),^[45] a height (in feet) representing the year of the United States Declaration of Independence.
• The 308 m (1,010 ft) Tour Generali in Paris La Défense, scheduled to be completed in 2013,^[46] is an entirely green building office skyscraper that is set to be the tallest building in Paris and the second tallest in the European Union after The Shard in London.^[46]
• Construction of The Shard in London started in March 2009, and is scheduled to be completed in May 2012, in time for the London Olympics.^[47][48] At 310 m (1,017 ft), it is set to be the tallest building in the European Union.^[49]

Sustainability

30 St Mary Axe in London is an example of a modern environmentally friendly skyscraper.

The skyscraper as a concept is a product of the industrialized age, made possible by cheap energy and raw materials. The amount of steel, concrete and glass needed to construct a skyscraper is vast, and these materials represent a great deal of embodied energy. Tall skyscrapers are very heavy, which means that they must be built on a sturdier foundation than would be required for shorter, lighter buildings. Building materials must also be lifted to the top of a skyscraper during construction, requiring more energy than would be necessary at lower heights. Furthermore, a skyscraper consumes a lot of electricity because potable and non-potable water must be pumped to the highest occupied floors, skyscrapers are usually designed to be mechanically ventilated, elevators are generally used instead of stairs, and natural lighting cannot be utilized in rooms far from the windows and the windowless spaces such as elevators, bathrooms and stairwells.

In the lower levels of a skyscraper a larger percentage of the building cross section must be devoted to the building structure and services than is required for lower buildings:-

• More structure – because it must be stronger to support more floors above
• The elevator conundrum creates the need for more lift shafts – everyone comes in at the bottom and they all have to pass through the lower part of the building to get to the upper levels.
• Building services – power and water enters the building from below and have to pass through the lower levels to get to upper levels.

In low-rise structures, the support rooms (chillers, transformers, boilers, pumps and air handling units) can be put in basements or roof space – areas which have low rental value. There is, however, a limit to how far this plant can be located from the area it serves. The farther away it is the larger the risers for ducts and pipes from this plant to the floors they serve and the more floor area these risers take. In practice this means that in highrise buildings this plant is located on 'plant levels' at intervals up the building.

Quotations

“

What is the chief characteristic of the tall office building? It is lofty. It must be tall. The force and power of altitude must be in it, the glory and pride of exaltation must be in it. It must be every inch a proud and soaring thing, rising in sheer exaltation that from bottom to top it is a unit without a single dissenting line.

”

—Louis Sullivan's The Tall Office Building Artistically Considered (1896)

See also

• Skyscraper design and construction
• Skyscraper Index
• Emporis Skyscraper Award
• Skyscraper Museum in NYC
• Skyline
• List of tallest buildings and structures in the world
• List of tallest buildings in the world
• Timeline of three tallest structures in the world
• List of cities with most skyscrapers
• Skyscrapers in film
• Groundscraper
• Vertical farming, "farmscrapers"
• Seascraper
• World's littlest skyscraper

References

1. ^ [1] For more on the origins of the term skyscraper, see "Skyscrapers," Magical Hystory Tour: The Origins of the Commonplace & Curious in America (1 September 2010).
2. ^ Ivars Peterson (5 April 1986). "The first skyscraper – new theory that Home Insurance Building was not the first". CBS Interactive. http://findarticles.com/p/articles/mi_m1200/is_v129/ai_4501450/. Retrieved 6 January 2010. ""In my view, we can no longer argue that the Home Insurance Building was the first skyscraper," says Carl W. Condit, now retired from Northwestern University in Evanston, Ill., and author of several books on Chicago architecture. "The claim rests on an unacceptably narrow idea of what constitutes a high-rise commercial building," he says."If there is a building in which all these technical factors—structural system, elevator, utilities—converge at the requisite level of maturity," argues Condit, "it's the Equitable Life Assurance Building in New York." Completed in 1870, the building rose 7-1/2 stories, twice the height of its neighbors. To lighten the building and keep costs down, engineer George B. Post used a primitive type of skeletal frame in its construction. A great fire destroyed the building in 1912" 
3. ^ Finniston, Monty; Williams, Trevor; Bissell, Christopher, eds (1992). "Skyscraper". Oxford Illustrated Encyclopedia of Invention and Technology. Oxford University Press. p. 322. ISBN 0-19-869138-6. "Modern skyscrapers such as the World Trade Center, New York, have steel and concrete hull-and-core structures. The central core–a reinforced concrete tower–contains lift shafts, staircases, and vertical ducts. From this core, the concrete and steel composite floors span on to a steel perimeter structure; a lightweight aluminium and glass curtain wall encloses the building. This type of construction is the most efficient so far designed against wind forces." 
4. ^ Data Standards: high-rise building (ESN 18727), Emporis Standards, accessed on line 16 October 2009.
5. ^ Data Standards: skyscraper (ESN 24419), Emporis Standards, accessed on line 16 October 2009.
6. ^ "Penza State University of Architecture and Construction; Before The Workshop (1) Tower". Fondazione-delbianco.org. 31 August 1939. http://www.fondazione-delbianco.org/seminari/default.asp?tiporiga=A1&idprog=14&label=. Retrieved 5 June 2011. 
7. ^ "Huge New Rogers Skyscraper Proposed". skyscrapernews.com. 3 December 2007. http://www.skyscrapernews.com/news.php?ref=1244. Retrieved 3 December 2007. "...their eleventh proper skyscraper, that is by definition buildings above 150 metres" 
8. ^ A.F.K.. "The Project Gutenberg eBook of The Cathedral Church of Lincoln, by A.F. Kendric, B.A". Gwydir.demon.co.uk. http://gwydir.demon.co.uk/PG/BellsLincoln/BellsLincoln.htm. Retrieved 5 June 2011. 
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10. ^ Strabo, 5.3.7
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12. ^ Papyrus Oxyrhynchus 2719, in: Katja Lembke, Cäcilia Fluck, Günter Vittmann: Ägyptens späte Blüte. Die Römer am Nil, Mainz 2004, ISBN 3-8053-3276-9, p.29
13. ^ ^{a b} Werner Müller: "dtv-Atlas Baukunst I. Allgemeiner Teil: Baugeschichte von Mesopotamien bis Byzanz", 14th ed., 2005, ISBN 978-3-423-03020-5, p.345
14. ^ Behrens-Abouseif, Doris (1992). Islamic Architecture in Cairo. Brill Publishers. p. 6. ISBN 90 04 09626 4. 
15. ^ Mortada, Hisham (2003). Traditional Islamic principles of built environment. Routledge. p. viii. ISBN 0700717005. 
16. ^ ^{a b} Old Walled City of Shibam, UNESCO
17. ^ Helfritz, Hans (April 1937). "Land without shade". Journal of the Royal Central Asian Society 24 (2): 201–16. 
18. ^ Shipman, J. G. T. (June 1984). "The Hadhramaut". Asian Affairs 15 (2): 154–62. doi:10.1080/03068378408730145. 
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20. ^ Manchester School of Architecture video YouTube
21. ^ Building Design Architect's website, 8 Jan 2010
22. ^ "Royal Liver Building". Encyclopædia Britannica. http://www.britannica.com/EBchecked/topic/511448/Royal-Liver-Building. Retrieved 23 June 2011. 
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Further reading

• Skyscrapers: Form and Function, by David Bennett, Simon & Schuster, 1995.
• Landau, Sarah Bradford; Condit, Carl W., Rise of the New York skyscraper, 1865–1913, New Haven : Yale University Press, 1996. ISBN 0-300-06444-6
• Willis, Carol, Form Follows Finance: Skyscrapers and Skylines in New York and Chicago. Princeton Architectural Press, 1995. 224 P. ISBN 1568980442

External links

• Historical photos of skyscrapers in New York City
• Skyscraper Museum
• Tallest Building in the World
• SkyscraperPage Technical information and diagrams
• AllAboutSkyscrapers.com Articles, Data and Photos
• Skyscrapercity Technical information and Project Update forum
• Skyscrapers at the Open Directory Project
• 1880s "skyscraper" citations from word researcher Barry Popik.