Castrojeriz village is considered one of the landmarks of historic interest in the Camino de Santiago. Its rich history may take up consideration as castro Visigoth, or perhaps, also, Roman fort, (they say was founded by Julius Caesar) in whose castle was developed important battles between Christians and Moors.
The first mention of this castle dates from the 9th century during the skirmishes with the Muslim forces. There are three clearly differentiated sections: the Roman part which is today reduced to an almost hidden square tower; the Visigoth part comprising the extension to the castle with different masonry work from in the Roman part; and the medieval part.
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.