11. Estonia's Rummu Prison
Rummu Underwater Prison, Estonia
Location: Rummu, Vasalemma Parish, Estonia
Year Established: 1938
Entry Fee: $3.10
Rummu is a unique underwater prison located in Estonia, distinguished by its unusual history. Originally a limestone quarry, it was converted into a prison camp in 1938 by the Soviet Union, which ruled Estonia until the 1990s. Inmates at Rummu were compelled to mine limestone as part of their sentences, contributing to the quarry's expansion. Over time, the quarry flooded, creating a striking underwater landscape that now surrounds the remnants of the prison.

Rummu Underwater Prison, Estonia
Following the collapse of the USSR in 1991, Rummu Prison was abandoned, leading to the rapid flooding of the quarry due to a lack of oversight. Today, the prison is completely submerged, transforming it into a popular destination for scuba divers. Adventurous divers are drawn to explore the remnants of the prison buildings and the mining machinery that lie beneath the surface, creating an intriguing underwater landscape.
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Keeps debt accumulation in check.
Sketching variations already.
Liberates focus for higher-order work.
Deserves a failure-mode annex.