Tolmin Castle, Castle ruin on Kozlov Rob hill, Tolmin, Slovenia.

Tolmin Castle is a fortress ruin on the ridge of Kozlov Rob above Tolmin. Its original core consisted of the east and north towers, and two hexagonal towers were added later. Parts of the structure have been restored, while other sections remain in ruins.

First documented in 1188, the castle passed through the hands of the Patriarchate of Aquileia, Counts of Gorizia, Venice, and Habsburg rulers. Each period of control left its mark on how the fortress was built and maintained.

The castle's chapel of Saint Martin is documented in 1194, making it one of the earliest named parts of the fortress. The castle itself served no civilian population in peacetime: only a garrison lived there, and the site also held a prison. The name Kozlov Rob, 'Billy-goat's Edge', is the ridge locals use for the hill above Tolmin.

The ruin stands on the Kozlov Rob ridge above Tolmin, reached on foot by a marked trail from the town. Parts of the structure have been restored, while other sections remain in ruins, so watch your footing on uneven ground. Allow time for the climb and for the walk along the ridge.

The north tower had a large basement for storing provisions, which together with two wells and rainwater cisterns let the garrison withstand sieges. The castle had no permanent civilian population in peacetime, only a large garrison, and it also housed a prison.