Kyjovský hrádek, also Horní Karlštejn and Pustý hrádek (German: Oberer Karlstein and Wüstes Schloss) is the name of the ruins of what is supposed to have been a rock castle (Felsenburg) near Kyjov (Khaa) in the Bohemian Switzerland in the Czech Republic. The site is in the Kyjovské údolí (Khaatal) valley on a rock terrace above the River Kirnitzsch (Křinice) and covers and area of 150 by 150 metres (490 by 490 ft). Beam supports and the remnants of rooms carved out of the rock are still visible.