Nutjak, Medieval castle ruin in Gardun, Croatia

Nutjak is a stone fortress ruin perched on a cliff about 339 meters (1,112 feet) above the right bank of the Cetina River, overlooking the surrounding landscape. The remains include a circular tower and standing walls that display the medieval fortification methods used in this area.

Nutjak was built at the end of the 15th century on the initiative of Žarko Dražojević (1438–1508), duke of Poljica, to protect the lands west of the Cetina from Ottoman incursions. It passed under Ottoman rule before 1513. Freed during the Morean War in 1685, it returned to Poljica, came under Venetian rule in 1701 and was rebuilt; after the Ottomans were expelled from Imotski in 1717 it lost its defensive role and decayed.

The stone structure displays military architecture typical of the period, with remains that reveal how builders constructed fortifications in this region. Walking around the site, visitors can see the practical layout of the fortification and understand how people adapted to this remote location.

The approach path leaves the Trilj–Bisko road at the fourth kilometre and climbs to the tower in about 15 minutes. The main entrance lies on the partly preserved western rampart, about 7 m long and 4 m high. The A1 motorway bridge over the Cetina stands close to the ruins.

Locals in Trilj and Gardun call the ruin simply "Kuletina", a name not found in the medieval sources. The site is registered as protected immovable cultural heritage under the designation Z-5289, classified as secular architectural heritage. Excavations led by Angela Tabak of the Museum of the Trilj Region have been running since 2006.