The Roman amphitheatre in Windisch was built in the first half of the 1st century AD in the immediate vicinity of the Roman legion camp Vindonissa. It is the largest ancient amphitheatre in Switzerland.
During the reign of Emperor Tiberius (14 to 37 AD), when the Legio XIII Gemina was stationed in Vindonissa, a first wooden amphitheatre was built. It was destroyed by fire around 45 AD.
The camp was rebuilt of stone around 50 AD by Legio XXI Rapax and it has been preserved until today. The outer wall was 111 × 99 meters, the arena 64 × 52 meters. There was space for around 11,000 spectators.
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.