Kieselstein Castle, also known as Khislstein, (Slovene: Grad Kieselstein / Khislstein) is a 13th-century castle in the city of Kranj, in the Upper Carniola region of Slovenia. The castle stands at what was once a defensible point, guarding the city pier and crossing over the river Sava, and was predated on the site by a round 11th-century keep. The current structure was built in 1256 by the Counts of Ortenburg, by an arrangement with the lord of Kranj, Ulrich III, Duke of Carinthia. Until 1420, the tower was managed by their ministeriales or vassals, the knights von Chreinburch; in that year, it passed to Count Hermann II of Celje. During the period of Turkish incursions, the tower was incorporated into the city walls. After the extinction of the Counts of Celje in 1456, it was inherited b