Monastery of San Juan de Duero, built in the Romanesque style, consists of a single nave with a wooden roof, semicircular apse, and a pointed barrel vault. From the 12th century it belonged to the Knights Hospitaller of Jerusalem, until it was abandoned in the 18th century. The 12th century church and the 13th cloister, with Gothic and Mudéjar elements, are still standing.The arcades combine the various architectural styles current in Spain at the time: late Romanesque, early Gothic, and especially, Islamic tracery. These arches are criss-crossed to achieve a beautiful visual effect. Inside the church there is a display of items from Jewish, Islamic and Christian cultures.
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.