Llantilio Crossenny was a manor of the Bishops of Llandaff in the Middle Ages, and the site of their manor house can still be seen at Hen Gwrt. Their episcopal presence and the proximity of White Castle account for the 'exceptional scale' of the church. It is of Old Red Sandstone with a shingled spire. The tower and the nave are of the thirteenth century whilst the chancel was rebuilt in the fourteenth. The spire was added in the early eighteenth century and the whole was restored by John Prichard and John Pollard Seddon in 1856–7.
Either side of the East window of the chapel are two stone corbels which are said to represent Edward II. The interior also has a number of seventeenth and eighteenth century funerary monuments of high quality and stained glass by Charles Eamer Kempe.
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.