Classified as a National Monument in 1910, it is the main ex-libris of the city of Bragança, and the only example of Romanesque civil architecture existing in the entire Iberian Peninsula. Its construction dates back most likely to the first third of the 400s, possibly coinciding with that of the castle. Some erudite authors, such as the abbot of Baçal, pointed to the end of the 12th century and the beginning of the 13th century as the time of its construction. But more recent studies point to the end of the 14th century as the most probable date of its construction, making it a later medieval Romanesque. The building has an irregular pentagonal plan and is formed by two distinct bodies (spaces): the underground, formed by a large semi-buried cistern in a rocky cavity, with a barrel vault reinforced by two transverse arches (to store rainwater) and springs, and the surface, which covers the cistern, and forms the paved floor of the hall, conceived as a large gallery fenestrated by 38 small semicircular arch windows, which give originality to the building. The entire building is constructed of granite and is covered by a five-sided roof, based on cornices, which are hollow on their upper side, with the purpose of capturing rainwater, which is then conducted to the cistern through channels open in the walls. The cornices are supported, both inside and outside the building, by 53 modillions carved with geometric, vegetal, zoomorphic, and anthropomorphic motifs, except one, inside, which has the coat of arms of Portugal represented. Two straight lintel portals, open on the North facade of the building, give access to the elevated interior of the gallery, with the masonry floor pierced by three quadrangular openings that give access to the cistern. Along the five interior walls runs a bench, or stone seat, which was expressly built to serve as a “Council”, and there meetings of “good men” were held to discuss the problems of the municipality. The Domus was restored (to its current appearance), recovering its original characteristics, with works promoted by the Directorate General of Buildings and National Monuments and designed by the Architect Baltazar de Castro, being inaugurated on October 23, 1932.