Galerias Romanas, Lisbon

Galerias Romanas is an underground architectural structure beneath Rua da Prata and Rua da Conceição, extending as far as Rua do Comércio in Lisbon’s Baixa. It is understood today as a cryptoporticus: a substantial artificial platform that helped support buildings on unstable ground. The surviving passages are vaulted corridors, about 3 metres high and about 2 to 3 metres wide, with smooth upright walls and rounded arch ceilings.

Their construction belongs to the period of Roman rule under Emperor Augustus, between the 1st century BC and the 1st century AD. The galleries came to light in 1770 during construction of a building on Rua da Prata. That work also uncovered a stone dedicated to Aesculapius, now held by the Archaeological Museum. Water normally fills the galleries; public visits take place only when it is removed for a short guided opening.