Roma Abbey was built in 1164 by Cistercian monks. The monks established a religious and agricultural centre for the entire Baltic Sea region. After the Reformation in the early 16th century, the monastery was abandoned. It was then under the Danish Crown. The monastery building was partly demolished and the church was used as a stable. In 1645, through the peace treaty in Brömsebro, Gotland became Swedish again.
In 1733, County Governor Johan Dietrich Grönhagen, build a new stately residence, using material from the old monastery in the construction. No major changes have been made since then. It was used as the residence for the County Governor until 1822. Today impressive ruins are well known for the Shakesperian plays that are performed here every summer.
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.