The Regenwurmlager, which literally means Camp Earthworm, is an extensive underground fortification area constructed by Germany in 1920s-1940s, now in western Poland, near the city of Międzyrzecz. It was a system of underground bunkers interconnected by tunnels and corridors of total length over 100 km. In 1945 it was abandoned by the German troops retreating without significant fights.

Growing up to 3 or 4 meters (13 ft.) in length with the body about 3 cm (1.5 inch) thick these awesome giant earthworms may easily be confused with snakes.