Zkamenělý zámek, Natural monument in Česká Cikánka, Czech Republic.

Zkamenělý zámek is a group of frost-riven rock crags of two-mica orthogneiss (biotite alkali-feldspar metagranite with muscovite) of the Svratka crystalline complex, rising to 768 m on a blind ridge of the Borovský les in the Žďárské vrchy. The summit rock wall is split into blocks named Skříň, Hlava, Spárová věž and Zámecká věž, with Hradiště and Rasovna on the slope and the lone crag Pivovar to the southwest.

Archaeological digs in 1887, 1889 and 1890 by Karel Adámek and his son Karel Václav Adámek found pottery shards, stone and iron objects, arrowheads and traces of a wooden structure on the summit. The site was a prehistoric and early medieval hillfort whose remains were later reused for a medieval castle. It has been protected as a natural monument since 1977.

The name Zkamenělý zámek ("petrified castle") appeared in the second half of the 19th century, when popular imagination saw a tower, window and stairs in the rocks. Earlier names were Karlštejn, Starý Karlštejn and the German kahler Stein, "bare stone", used by forest staff of the Rychmburk estate.

The rocks stand 3 km east of Svratka at 765–768 m, reached on foot from the Svratka valley; the summit wall is enclosed on the east by an earth bank and a double rampart. The site has been a protected natural monument since 1977, so stay on the paths and leave the rock and the ramparts as they are.

The "window" is not a hole through rock but the wide fissure between the blocks Zámecká věž and Hlava, which villagers of Česká Cikánka read as a castle window. The stepped gap between Hlava and Skříň they called the stairs into the castle.