Rio Dão

Rio Dão or river Dão is a Portuguese river that originates in the plateau regions of Trancoso-Aguiar da Beira in the Eirado parish, Aguiar da Beira council, District of Guarda, and varies between 714 meters and 757 meters in elevation.

It flows in a general NE-SW direction, passing through Barragem de Fagilde and crosses or demarcates the limits of the councels of Aguiar da Beira, Penalva do Castelo, Mangualde, Viseu, Carregal do Sal, Nelas, Tondela, and Santa Comba Dão. It empties into the Mondego river, in the limits of the councils of Santa Comba Dão, Mortágua, and Penacova, after covering about 100 kilometres.

Its main tributaries are the River Carapito, Ribeira de Coja, River Sátão and the River Criz. Its granite-sloped valley is situated in the "Região Demarcada do Dão", where the Vinho do Dão table wines are produced.