St Cynog's Church in Defynnog contains an ancient stone with Ogham inscriptions. Though most of the attractive building we see today is 15th century, the origins of St Cynog's go back to at least the Norman period if not earlier. There is 11th century stonework in the north vestry wall, and the font and holy water stoup may be 11th century or possibly even pre-Norman. The richly carved font is inscribed with Runic letters, the only example in Wales of a Runic inscription.
The churchyard contains several yew trees, of which the largest has a girth large enough for it to be 1300–3000 years old. An adjacent yew was reported in 2014 to be genetically identical to the largest, leading to conjecture in the popular press that the two trees were remnants of a single 5000-year-old tree; but this conjecture has been disputed on the grounds that layering is a more plausible origin for the adjacent tree. The crown of the largest tree is 60 ft in diameter.
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.