Dolnośląskie·Poland
Photo: ARKADIUSZ MARKIEWICZ · Wikimedia · CC BY-SA 3.0
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.
In season: Year-round
Project Riese is the largest unexplained construction project of the Second World War — seven complexes bored into the Owl Mountains from 1943 using prisoners from Gross-Rosen, with no surviving document saying what any of it was for. Work stopped in 1945 and it has been sitting there since.
Osówka and Włodarz are open with guides, and parts are flooded and toured by boat. The scale underground is genuinely unsettling, and the history is grim rather than adventurous — worth knowing before you go.
It is a constant six degrees below ground in low light, while the mountains above make a decent walking day if you want daylight afterwards.
The most complete guided route, machinery still in place
The largest accessible section, unfinished halls and corridors
Flooded tunnels crossed by boat
Access is by guided tour only, and tours run year-round, so book a slot at one of the open complexes — Osówka, Włodarz or Rzeczka — rather than trying to enter independently. Take a warm layer regardless of the season outside; it holds around six degrees underground all year.
Some sections are flooded and done by boat, so expect damp. It is an easy weekend from Wrocław, about 70 km, and suits older children and up. Pair the underground tours with a walk in the Owl Mountains above for daylight and contrast.
Go in with the history in mind — this is a sombre site, not a thrill ride.
Listed because they’re local and run this themselves. We take no commission.
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