Project Riese ("Giant") was a massive Nazi construction project during WWII (1943-1945) to build huge underground complexes and tunnels in the Owl Mountains (Góry Sowie) and near Książ Castle in Lower Silesia (now Poland) for military, industrial, and possibly Hitler's headquarters, using forced labor, with remnants now open as tourist attractions like Osówka, featuring unfinished tunnels and structures. Key Aspects: Location: Owl Mountains (Góry Sowie) and Książ Castle area, Lower Silesia, Poland. Purpose (Debated): Speculated to be for a superweapon factory, command centers, or a new Führer headquarters, but never fully completed or used as intended. Scale: A vast network of tunnels, halls, and structures built into the mountains. Labor: Built by forced labor, including prisoners from concentration camps. Legacy: Some sites, like Osówka, are accessible to the public, offering historical tours and extreme explorations, revealing the scale of the unfinished project. Key Sites: Osówka: One of the most famous and accessible Riese sites, offering historical and extreme routes. Walim Drifts (Rzeczka): Another significant part of the complex, with tunnels open to visitors. Książ Castle: Connected to the complex via underground tunnels, with parts of its own underground world integrated.