Probably built in the first half of the 12th century (although some legends say it was built in the 9th century), Sandiás Castle was located over a castrum (Celtic settlement). It participated in the Portugal secession wars (12th century). In 1386 it was assaulted by the duke of Lancaster, pretender to the Castile crown. In the 15th century it was demolished by a popular riot, and rebuilt later. It was a meeting point for troops in the wars with Portugal in the 18th century. There are many legends about this castle.
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.