Karlštejn (German: Karlstein) is a large Gothic castle founded in the 14th century by Charles IV. The castle served as a place for safekeeping the Empire coronation jewels, holy relics and other royal treasures. Located about 20 km southwest of Prague in the Karlštejn village, it is one of the most famous and heavily visited castles in the Czech Republic.
The castle was founded in 1348 by the Czech king and Holy Roman Emperor Charles IV who personally supervised the construction works and the decoration of interiors. The construction was finished nearly twenty years later when the "heart" of the treasury – the Chapel of the Holy Cross situated in the Great tower – was consecrated in 1365. With the outbreak of the Hussite Wars, the Czech coronation jewels were moved to the castle and were kept there for almost two centuries, with some short-time breaks.
The castle underwent several reconstructions: in late Gothic style after 1480, in Renaissance style in the last quarter of the 16th century and finally a neo-Gothic reconstruction between 1887 and 1899 carried out by Josef Mocker that gave the castle the present look.