Laubenbergerstein is a hilltop castle, likely established in the 12th century by the Bishops of Augsburg, aimed to safeguard the crucial Iller River crossing and associated customs station. Initially occupied by the Laubenberg family, the castle experienced conflicts, including attacks in 1449 by Graf Hugo XIII. von Montfort. Kaspar von Laubenberg initiated substantial expansions after 1450, resulting in the dominant artillery keep. During the German Peasants' War in 1525, the castle was seized and weapons were stolen.
In 1559, the Laubenberg family left the castle for a newly built residence in Rauhenzell. By 1629, the castle was already considered a partial ruin. Margaretha von Laubenberg accelerated its decay in 1641, selling roofing tiles. In 1647, the fief was revoked, and by 1806, the castle came under Bavarian rule. In 1977, the Immenstadt Heritage Association acquired the ruins and began restoration efforts. The castle, made of local materials, is now accessible to visitors. The imposing artillery tower, constructed after 1450, dominates the castle's appearance and can be climbed on special occasions.
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.