Planina Castle, Castle ruin in Planina pri Sevnici, Slovenia

Planina Castle (Grad Planina, German Montpreis) stands in ruins above the market town of Planina pri Sevnici in the Šentjur pri Celju municipality. The castle was built on a hill, not on the plain, and its remains overlook the surrounding landscape. The core of the structure shows Romanesque features with Gothic elements visible in the southern wall, Renaissance details at the entrance and northwestern defensive wall, while the lower courtyard and residential tower remain visible.

The castle was first documented in 1190 and played a role in the region's medieval politics. In 1341 it came into the hands of the Counts of Celje after Ulrich of Sanneck acquired it from the lords of Ptuj.

The castle's German name, Montpreis, appears in the 13th-century epic Parzival by Wolfram von Eschenbach. The Slovene-born writer Ana Wambrechtsamer (1897–1933), from the nearby market town of Planina, set her historical novel "Danes grofje Celjski in nikdar več" here.

The ruins stand on a hill above the market square of Planina pri Sevnici, in the Šentjur pri Celju municipality, so the final approach is uphill on foot. The site is a monument of local significance and lies in the open, without visitor facilities. The terrain around the collapsed walls is uneven, so wear sturdy shoes.

The lower sections of the castle wall feature an opus spicatum pattern, a distinctive herringbone design made with stone that resembles grain spikes. This medieval craftsmanship detail is one of the most recognizable aspects of the structures visible today.