Fort Vechten was constructed between 1867 and 1870 as part of the so-called Nieuwe Hollandse Waterlinie (The 'New Dutch Water Line') to defend the cities of the western Netherlands from overland attack.
The history of Vechten dates however back to the Roman times. The Romans, who apparently chose the spot because it controlled a side-arm of the Lower Rhine, built their castellum by the year 4 AD, and possibly named it after that river, Fectio. This fort was quite important from time to time as a supply-base for the invasion of Germany. It attracted the local population as well, which came to settle in the vicus at either end of the fort. The castellum was most likely abandoned by the late 3rd century, when the Roman Empire faced crisis after crisis. However, the main reason that the army never returned may well have been because the access to the fort silted up, which caused it to become land-locked, with all the ensuing logistical problems. The neighboring castellum at Trajectum/Utrecht may have supplanted it as local fort. Today there is a reconstructed Roman watch tower.
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.