Ključica is the largest and best preserved medieval fortress in Krka National Park.
It was erected by the Croatian noble Nelipić family in the 13th century over the canyon of the Čikola River in order to protect their estate from their rivals, the noble Šubić family. Due to its strategic position, Ključica was often a source of conflict for its masters, the Šibenčani.
In 1546, it was conquered by the Turks who ruled here until 1648 when they were finally forced out. Since then, Ključica has been abandoned and no one ever lived here again.