Pauline Cave Church Welcome Center

In the 1920s, Catholic monks built this church in a large cave system previously used by a hermit monk. Known as Saint Ivan's Cave, the cave was used as a hospital during World War II. After the war, when the communists came to power, they sealed the entrance with concrete and executed the head monk. In 1989, with the fall of the Iron Curtain, the church was reopened and is now a popular spot for tourists as well as a place of worship for locals. One of the coolest churches I've ever seen, a bit like the rock church in Helsinki, this still-functioning church is carved into the cave systems of Gellért Hill. The audio guide is definitely worth getting.