Regenwurmlager, Military fortress in Międzyrzecz, Poland
Regenwurmlager is an extensive underground fortification system consisting of roughly 100 concrete structures connected by approximately 32 kilometers of tunnels reaching depths of around 40 meters. The complex includes barracks, workshops, and specialized military installations throughout its network.
German engineers built this fortification system between 1934 and 1944 as part of a defensive strategy to protect Berlin's eastern approaches during World War II. The construction reflected the military preparations of that era.
The fortress displays its military past throughout the complex, with gun positions, ammunition storage areas, and underground stations still visible. Visitors can walk through these spaces and see how soldiers lived and worked in this underground world.
Two designated museum entrances provide access to the complex, where guided tours navigate the underground network. The subterranean passages can be challenging, so visitors should be prepared for demanding walking conditions.
The tunnel system has become Europe's largest bat hibernation site, sheltering approximately 39,000 bats of various species during winter. The former military fortress transformed into a sanctuary for wildlife.
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