Tuwaiq

Jebel Tuwaiq (pronounced "Twayg", _ar. جبل طويق) is a narrow escarpment that cuts through the plataeu of Nejd in central Arabia, running approximately 800 km from the southern border of Al-Qasim in the north, to the northern edge of the Empty Quarter desert near Wadi ad-Dawasir in the south. The eastern side slopes downwards gradually, while the western side ends in an abrupt manner. The escarpment can be thought of as a narrow plataeu, though the locals refer to it as a "jebel", or "mount".

Many narrow valleys ("wadis") run along its sides, such as Wadi Hanifa, and a group of towns lie on its central section, including the Saudi capital, Riyadh. Many settlements have historically existed on either side of it as well, such as those of Sudair and Al-Washm. The Tweig escarpment is mentioned in Yaqut's 13th century geographical encyclopedia under the name Al-'Aridh, though for the past few centuries that name has applied only to the central section of it, around Riyadh.