Tolmin Castle was first mentioned in 1188, and its chapel of Saint Martin in 1194. The east and north towers appear to have formed the original core of the fortress; another two hexagonal towers were added later. The north tower had an extensive basement for the storage of provisions, which along with two wells and rainwater cisterns allowed for the withstanding of sieges.
The castle was held in fief by a long series of masters: the Patriarchate of Aquileia, the Counts of Gorizia, the city of Cividale del Friuli, the Venetian Republic, and finally the Habsburgs. It appears to have functioned as a dedicated fortress rather than a residence, and had no permanent civilian population in peacetime, only a large garrison; it also housed a prison. The structure was severely damaged in the earthquakes of 1348 and 1511, but was repaired each time. It was finally abandoned in 1651 by its last owners, the Coronnini family, for a new manor in Tolmin itself, though it remained sufficiently intact by 1713 to play a role in the great peasant revolt of that year. The castle is currently in ruins, though parts of it have been restored.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.