Karlštejn Castle, founded in 1348 by Charles IV, King of Bohemia and Holy Roman Emperor, served as his private residence and a secure place for royal treasures, including holy relics and the Imperial Crown Jewels. The castle features Gothic and Renaissance architectural styles, with significant reconstructions in the 19th century. Notable elements include the Chapel of the Holy Cross and the preserved original stair-arrangement. The castle remains a prominent historical site in Czechia.