The Moscow Times
During [the] Soviet times, the Rummu quarry in Estonia was used as a mining site for Vasalemma marble and most of the workforce came from among the detainees of the nearby Murru prison.
When the prison closed after 1991, pumps that once kept the quarry and the prison dry were shut down, causing water to fill the quarry.
It has become an unofficial and unguarded swimming and diving spot, attracting locals and tourists alike.
View photo and the original article here:
Estonians Swim in Flooded Soviet Prison