Riese ([ˈʁiːzə]; German for "giant") was the codename given to a construction project undertaken by Nazi Germany between 1943 and 1945. Consisting of seven underground structures at Książ Castle and in the Owl Mountains in Lower Silesia, which was then Nazi Germany and is now Poland. None of the structures were finished, and all are in different states of completion with only 11% reinforced with concrete. The purpose of the project remains uncertain due to a lack of documentation. While some sources suggest that all the structures were part of the Führer Headquarters, others claim that it was a combination of headquarters (HQ) and arms industry facilities. However, comparison to similar facilities indicates that only the castle was adapted as an HQ or official residence, while the tunnels in the Owl Mountains were planned as an underground factory complex. Construction work was carried out by forced labourers, prisoners of war (POWs), and concentration camp prisoners, many of whom lost their lives.