The Trier Imperial Baths (Kaiserthermen) are a large Roman bath complex, designated as part of the UNESCO World Heritage Site. The impressive ruins of the baths, along with the derelict rooms and the walls of previous structures, are among the most important to have been discovered in Trier. Today a visit to the thermal baths, which can also be explored below ground, is like stepping back in time. The walls of the hot bath (caldarium) are deservedly part of this famous landmark in Trier. After the one in Rome, the Imperial Thermal Baths and St. Barbara Roman Baths were once among the largest bathing complexes in the Roman empire. They were built in the first and second centuries AD.
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.