The Osówka Complex was part of a project conducted by the Nazi Germany between 1943 and 1945 (code name Riese). The mysterious structure known as the underground city still hasn't revealed all of its secrets. Discover the biggest and the most complex Hitler headquarter in Lower Silesia.  Ksiaz Castle is the third-biggest castle in Poland situated in the majestic rock cliff aside the Pelcznica River. Located 395 meters above sea level and surrounded by a beautiful forest, the castle is sometimes called the Pearl of Lower Silesia. The castle's location combined with its size is not a common sight in Europe. In 1943 Hitler's paramilitary organization began building one of his main quarters which, along with other objects of the Riese complex close to the castle near Osowka and Wlodarz played a crucial role. Gross-Rosen in Rogoźnica is the largest Nazi-German concentration camp in Lower Silesia, with particularly harsh conditions and penal work in the quarries. The motto of this place was 'Vermichtung durch Arbeit' (Annihilation through work). Around 40000 prisoners died here incleding Poles, Jews, Russians, French and Hungarians.