Budapest is the only Capital in the world with show caves right in the middle of the city! It was even named after the caves. The castle of today stands on Gellért Hill, a limestone hill riddled with caves. When city was conquered by the Magyars from Asia, they saw a hill with a huge hole and many caves inside. Their own language had no word for cave, so they borrowed the Slavic word pest from the locals. They named what is now Gellért Hill buda pest (hill of caves).
In 1926 a lovely chapel was built inside the hollow of Gellért Hill. It is tiday known as Szent Gellért plébania or simply Rock Chapel.
All the caves are in a part of Budapest, called Rose Hill. The limestone in this area was formed in the Eocene, 34 to 55 Million years ago.
The caves were formed by thermal water. Thus the solution was very fast, much faster than in cold water caves. Also this water brought dissolved minerals into the caves. Those minerals formed extraordinary speolethems. Even the calcite was deposited in his second crystal structure, which is formen in warm water, called aragonite.
Some parts of the cave system are show caves, other caves have served as wine cellars or air raid shelters. The hot water from the springs is used in numerous spas all over the city center. Even some caves are used for bathing.