The Château du Grand-Geroldseck is a ruined medieval castle situated in Haegen, Alsace. The castle is one of the oldest in the northern Vosges, founded at the beginning of the 12th century by the lords of Geroldseck, avoués of the abbey of Marmoutier, to ensure the protection of its territories. It constitutes a fine collection of feudal residence. Built on a platform, it combined the functions of dwelling and defence. It was heavily altered at the 13th, 14th and 15th centuries.
The square keep has walls three metres thick, faced in embossed stone. The cellars of the lord's residence and the barbican are still visible.
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.