Urban exploration in Góry Sowie

Project Riese is the largest unexplained construction project of the Second World War. Seven complexes were bored into the Owl Mountains from 1943 using prisoners from Gross-Rosen, and no surviving document says what any of it was for. The work stopped in 1945 and it has been sitting there ever since.

Osówka and Włodarz are open with guides. Parts are flooded and toured by boat. The scale underground is genuinely unsettling, and the mountains above make a decent walking day if you need daylight afterwards.

Constant 6°C underground, low light, and a site whose history is grim rather than adventurous.

Guided tours only and they run year-round. Take a warm layer regardless of the season outside.