Orivirran saarto is a ruin of the 16th century fortress. It was built probably in 1540's, because in 1546 Russians complained about Swedish cutting forest and gathering stones in Orivirta. There were probably a main castle, outer fortication, watchtower and dock. During 16th century it was garrisoned by 400-600 men and 5-10 cannons.
In 1592 Russian cossacks destroyed the fortress. In a fight over 200 men were died and Swedish lost a ship and several cannons. After defeat Orivirran saarto was changed to guard place and fortified again during the Russo-Swedish War in 1656–1658.
Nowadays there remains some ruins of the fort restored by the Finnish National Board of Antiquities. There's also a memorial erected in 1965.
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.