Fortress Kostajnica was built most probably in the 14th century and owned by the members of the noble families Frankopan, Lipovečki, Tot, Benvenjud and finally (in the 16th century) Zrinski, so it is today also known as Zrinski fortress or castle. It was conquered by the Ottomans on 17 July 1556, but it was freed from their rule relatively fast, in 1688.
Situated on the bank of the river Una, the fortress has very strong walls and three towers. Having been in pretty bad shape before, it has been renewed in the recent years by the Croatian Ministry of culture.
References:The Beckov castle stands on a steep 50 m tall rock in the village Beckov. The dominance of the rock and impression of invincibility it gaves, challenged our ancestors to make use of these assets. The result is a remarkable harmony between the natural setting and architecture.
The castle first mentioned in 1200 was originally owned by the King and later, at the end of the 13th century it fell in hands of Matúš Èák. Its owners alternated - at the end of the 14th century the family of Stibor of Stiborice bought it.
The next owners, the Bánffys who adapted the Gothic castle to the Renaissance residence, improved its fortifications preventing the Turks from conquering it at the end of the 16th century. When Bánffys died out, the castle was owned by several noble families. It fell in decay after fire in 1729.
The history of the castle is the subject of different legends.