The present structure of Trinitatis Church was consecrated in 1690 and built in a late medieval style. A few decorated stones are included in the foundations, which come from a medieval church that was pulled down shortly after the setting up of Fredericia as a fortified town around 1650. The Romanesque font comes from the same source and along with a Baroque font canopy, is one of the church`s treasures. The majority of the interior is otherwise influenced by the late Baroque style. There are several memorials in the cemetery that are of significance for military historians.
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.