Castelseprio or Castel Seprio was the site of a Roman fort in antiquity, and a significant Lombard town in the early Middle Ages, before being destroyed and abandoned in 1287. It is today preserved as an archaeological park.
Castelseprio originated as a Roman fort that commanded an important crossroad. During the early Middle Ages, the Lombards occupied the Roman fort, turning it into a fortified citadel or small town. At one point coins were minted there - a sign of its importance. The Church of Santa Maria foris portas ('foris portas' meaning 'outside the gates' in Latin) which contains the famous frescoes, lay just outside the walls of the citadel. The early dedication of the church to Mary is an assumption; the first documented mention of a church dedicated to Mary in Castelseprio comes from the 13th century.
The whole citadel was completely destroyed by Ottone Visconti, Archbishop of Milan, after he captured it in 1287, to prevent it being used again by his rivals. Investigations into the church, which began in 1934, finally uncovered the famous Byzantinesque frescoes below later plaster in 1944.
The whole area is now an archaeological zone containing the remains of the walls and of the much larger three-aisled 5th-century Basilica of San Giovanni Evangelista. There is also a baptistry of the 5th to 7th centuries dedicated to St. John the Baptist. This has two fonts, perhaps for the use of different Rites, and is octagonal with a small apse to the east. A third Church of San Paolo has a central hexagonal plan and was built between the 6th and 12th centuries. There are some ruins left from the castle. Nearby is a large tower, once used as a convent.
The fame of Castelseprio lies in the Early Medieval frescoes contained in the small Church of Santa Maria foris portas. These frescoes are of exceptional rarity and artistic significance. Hidden for centuries, the frescoes were only rediscovered in 1944. In 2011, the church - and the castrum with the Torba Tower - became a UNESCO World Heritage Site as part of a group of seven inscribed as Longobards in Italy, Places of Power (568-774 A.D.)
When the Church of Santa Maria foris portas was investigated in 1944, it was found to contain, as well as later frescoes, a highly important and sophisticated cycle of fresco paintings showing very strong Byzantine influence. The dating of the frescoes and the origin of their painter or painters remain controversial, although the first half of the 9th century seems to be emerging as the most likely date.
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.