Prem Castle dominates the village and road, which winds around the top of the hill. It reigns over the viewing peak above the Reka Valley, the road across the valley and the traffic along the Reka River. The castle was built before 1213. After the Udo Knights there were many owners, among them the Walseeis, Hallers, Habsburgs, and Porcia Dukes. This compact two-storey building with a ground plan in the shape of the letter L has a Romanesque nucleus with an extension and a smaller yard protected with a wall.  The inner yard was decorated with Renaissance arcades. In the middle of the yard stands a small well.  The entire structure is additionally protected with exterior Renaissance walls and cylindrical towers. A large cistern stands in the larger courtyard, between the castle and the exterior walls.
 
The area on the ground floor of the castle is cross rib-vaulted. Above it is the castle chapel, which was set up at the end of the 14th century. Modest console masques in it are reminiscent of Parler workshops. A large hall on the upper floor decorated with a wooden promenade gallery was rearranged before the last war by its owners, the Zuccolini family from Trieste. It was painted with unusual decorative frescoes on a dark background.

The castle houses some modest local collections. The cylindrical towers of the outer walls have been arranged.  The keys are in a nearby house.