Cangas de Onís, capital of the area of the same name, sits in the valley formed by the rivers Sella and Güeña.

The most representative feature of the town is its Roman Bridge, declared to be a Historic-Artistic Site in 1931.It has five arches, three of them pointed, and from the centre hangs a reproduction of the Victoria Cross. The hermitage of Santa Cruz also stands out due to the age of the structure, built on a dolmen in 437. It was rebuilt by King Favila in 737 to guard the Victoria Cross. The last rebuilding work was carried out after the Spanish Civil War, and uncovered the dolmen, which dates from 3,000 BC. Other interesting buildings are the City Hall, from the late 19th century; the Cortés palace, in the Renaissance style; and the Chapel of San Antonio, from the 16th century.