Ismantrop is an ancient fortress, which was used probably between years 300-500 AD. The ringfort consists of a limestone wall approximately 300 meters long and has nine gates. Inside the ringfort were 95 houses arranged in 12 blocks around a central open area with a circular building. Ismantorp is the largest and probably the oldest of the ringforts on Öland.
The first written description of Ismantorp dates back to the year 1634. Renowned botanist Carl von Linné, as well as other travellers and scholars, paid attention to the fortress. Researchers have tried to determine the fortress's age, function and history since the 19th century. Its well-preserved walls distinguish the fortress, as do the central building's unusual location on a ground elevation, the 88 visible house foundations and the nine gates.
Theories of Ismantorp's function differ widely. The fortifications suggest a defensive purpose, but its many gates make is difficult to defend. Ismantorp fortress has been compared to large Slavic castles that were both protective fortress and religious sanctuaries. Other researchers view the fortress as an integrated part of a united defence of the island of Öland.
Ismantorp, which today is surrounded by marshes in the Mittlandskogen forest, is an archaeological enigma as well as a popular place to visit.
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.