The Tržan Castle is a ruined medieval castle above the village of Modruš in the northern part of historical Lika region, central Croatia. Before the administrative seat of the former Modruš County, it is today just a ruin in the Josipdol Municipality in the southern part of the Karlovac County.
Having been built on a ridge of a steep hill 670 metres above sea level on the eastern slopes of the Velika Kapela mountain, the castle was at a strategic place overlooking the road that connected the Adriatic Sea and the Pannonian Basin since ancient times. The road in question connected the Roman towns of Senia and Siscia. It was later, during the 18th century, reconstructed, improved and renamed as Josephina road.
Address 47303, Croatia
Coordinates 45°8'55.279" N 15°14'47.891" E