In the neighborhood of the fort of Rainau-Buch, the remains of several other Roman buildings are visible. For instance, there is the ruin of a monumental gate in the limes wall near the modern village of Rainau-Dalkingen, about a kilometer north of the fort. Originally, it was a wooden construction, but it was rebuilt several times.
In the final phase, at the beginning of the third century, it must have had a façade like the stage of a theater, with rather plumb columns. In the upper part of the gate, there must have been a bronze statue of an emperor, perhaps Caracalla, who defeated the Germanic tribe of the Alamans in 213, and may have started his campaign from Dalkingen. Twenty years later, the Alamans stroke back, and the gate was burned down.
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.