San Vincenzo in Prato is the only church in Milan which has entirely maintained its original Palaeo-Christian appearance. The first church was founded by the Lombard king Desiderius in 770, who dedicated it to the Virgin Mary. Later it was entitled to St. Vincent, when the latter's relics were found in an urn in the crypt, together with those of St. Quirinus and St. Nicomedes (859) and St. Abundius. The name in Prato derives from its location in the 'pratum' (in the field) area owned by bishop Odelpertus.
In 806 a Benedictine convent was added to the church; in the late years of the same century and in the early 10th century the church, in dismaying conditions, was rebuilt, but with similar appearance. The octagonal baptistery on the exterior, on the left, was built by architect Paolo Mezzanotte in year 1932, and includes a column-shaped font called Pietra santa (the Saint Stone) coming from the ancient church of S. Nazaro in Pietra Santa, which was demolished in year 1889 during the construction of the new Via Dante. The convent was suppressed in 1520 and in 1598 the church was restored and turned into a parish.
The basilica measures c. 40 x 20 m, and is in brickwork. The interior is on a nave and two aisles with wooden spans ceiling. The columns are from different ages. The elevated choir ends with a large apse. Under the presbytery is the crypt, which has also a nave and two aisles divided by ten small columns with sculpted capitals.
San Vincenzo lies on the founding of a Roman temple or oratory built along the way to Vigevano probably dedicated to Juppiter, which was located within a Roman necropolis (of which some remains are visible in the external left walls of the church).
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.