Ključica Fortress, also known as Ključ, is strategically positioned on the right bank of the Čikola River canyon. Its construction is attributed to the Croatian noble family Nelipić, who controlled the Miljevci Plateau area during the 13th and 14th centuries. The first indirect mention of the fortress dates back to 1333, when Izan Nelipić of Ključ is mentioned. Throughout history, Ključica was a site of conflict, including attacks by the people of Šibenik in the 14th century, which damaged but did not destroy it. Under a peace treaty in 1345, the Nelipići were required to demolish a new tower, and the fortress later passed into the possession of the Nelipići of Cetina.

‍

‍

Ključica is rectangular in shape and consists of a citadel and a walled outer bailey. Within the fortress, the remains of a multi-story palace and auxiliary rooms have been preserved. The bailey wall is largely intact, including the courtyard gate and the remains of a fortified gate in the southwest corner. Archaeological test excavations have been conducted in the southeastern and northern parts of the fortress. Findings include local pottery, fine majolica from the 13th to 15th centuries, fragments of Gothic architectural elements, glass, stone projectiles, and metal objects, primarily forged iron nails.

‍

‍

At the beginning of the 16th century, the region was exposed to Ottoman incursions. Around 1522, the Turks captured Ključica, which remained under their control until the Cretan War in 1648. After being reclaimed, the fortress was abandoned due to its loss of strategic importance. Its inaccessibility has contributed to its preservation to this day. Today, Ključica is accessible to visitors as a historic site within Krka National Park, offering insight into the medieval architecture and history of the region.