Gormaz was the largest fortress in Europe after its expansion in 956 AD. It is without a doubt the greatest example of military architecture, not only in Soria but in the entire Spanish territory. The original castle was built shortly after 756 AD by emir Abd ar-Rahman I of Córdoba, as part of a state ('dawla') policy to control rich landowners and peasants, as well as to try to govern and protect the Central Marches in the Douro Valley against the Christians to the North. In 965, Caliph al-Hakem II rebuilt and expanded the castle, as attested by an inscription over one of the gates.
The castle is more than 390 metres long though only 10-40 metres wide, has 28 towers, a main gate with a monumental horseshoe arch with remains of painted red and white voussoirs, two posterns, one of which with a small horseshoe arch, three mihrabs corresponding to a 'musalla' or open air collective oratory, use of 'spoliae' of the Roman period, and the remains of a water pool near the monumental gate mentioned before. It was repaired in the 14th century, from which time date the remains of two gates on the southern side.
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.