Monastery of Serra do Pilar
Santa Marinha e São Pedro da Afurada, Portugal
The Monastery of Serra do Pilar is a former monastery located in Vila Nova de Gaia, Portugal, on the opposite side of the Douro River from Porto. The monastery is situated on an outcrop overlooking the Dom Luís I Bridge and the historic centre of Porto. Together with these locations, the monastery was designated a UNESCO World Heritage Site in 1996. The monastery is notable for its church and cloister, both of which are circular.
Monastery data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).