The origins of Randeck Castle are unknown, but in the tenth century Duke Arnulf may have built built the first medieval fortress on the hill in order to protect the land against the raids of the Hungarians.
Baron von Rotteneck is said to have built the castle in the 11th century. In the 13th century the Counts of Abensberg took possession of the castle. The owner Jack von Abensberg was known as robber baron and the city of Nuremberg waged war against him. In 1446 his castles were demolished and burnt down. Niclas, the last Count of Abensberg, was killed in 1485 in a feud with a neighbouring family.
The castle was attacked by Swedish army during the Thirty Years´ War. Both castle and convent were destroyed. In 1838 a large part of the castle just collapsed after heavy rainfalls.
References:From its origin as a small stronghold built by the ancient Illyrian tribe Dalmatae, becoming a royal castle that was the seat of many Croatian kings, to its final development as a large fortress during the Ottoman wars in Europe, Klis Fortress has guarded the frontier, being lost and re-conquered several times. Due to its location on a pass that separates the mountains Mosor and Kozjak, the fortress served as a major source of defense in Dalmatia, especially against the Ottoman advance, and has been a key crossroad between the Mediterranean belt and the Balkan rear.
Since Duke Mislav of the Duchy of Croatia made Klis Fortress the seat of his throne in the middle of the 9th century, the fortress served as the seat of many Croatia"s rulers. The reign of his successor, Duke Trpimir I, the founder of the Croatian royal House of Trpimirović, is significant for spreading Christianity in the Duchy of Croatia.