Saint Aignan Church was originally built around year 400, in the era of pre-Romanesque, by the bishop of Chartres - later his name has given as the name of the church. The church is considered as the most ancient parishes in Chartres. In its history, the church has suffered from several times fire in 12th, 13th and in the early 16th century. Most of the church was rebuilt after the latest misfortune in the 16th century.
The main portal in the center of the front facade was the only part of the church that preserved for the new church. The church also suffered several times of change function during the French Revolution - it was once served as a military hospital, then once became a prison and even as a fodder shop. It finally returned as a worship place in 1822.
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.