The Church of Saint Thyrsus (Iglesia de San Tirso) was established in the 790s. Dedicated to Saint Thyrsus, it was built by Tioda, the royal architect of Alfonso II of Asturias. The Great Fire of Oviedo in 1521 and rebuilding in the 18th century removed most of the original church, except for a three-light window.
The building has suffered so much from alterations over the centuries and only the general plan has been preserved. It is that of a basilica with nave and aisles divided by rude stone piers set at unequal intervals, from which round arches spring. In the easternmost bay, however, owing to the smaller span, the arch was made sufficiently pointed to raise its crown to the same height as the others. This irregularity was already typical of Imperial Roman times, when barrel vaults were given a pointed form in order to make the height of rooms of varying size uniform, as it was necessary to raise the crown of the vault in some of them. This is illustrated by various chambers in the House of Tiberius on the Palatine.
There is no satisfactory explanation of the 'many angels' the building is said to have presented in the Codex Vigilianus.
In the rectangular sanctuary atriplet round-arched window 2 by 2 metres is preserved. With its pre-romanesque bases, rough brick arches, and capitals with rude packed leaves, it gives an idea of the better style of building and carving in the time of Alfonso II of Asturias. It is known that the church of San Tirso housed Royal Chapel.
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.