Under the Aosta old parish church, archaeological diggings brought to light the early Christian cruciform basilica, indicated as Concilium Sanctorum, the Assembly of Saints because it was built on the tombs of some of the early martyrs who were buried in the Roman cemetery area which in itself was built on a protohistoric funeral settlement.
Inside you can see parts of the liturgical structures, the relic platform with the tombs of three bishops who lived between the 5th and 6th centuries (Grato, Agnello, Gallo) and other tomb chambers dating from between the 5th and 8th centuries.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.