The oldest surviving parts of the St Mary's Church are the chancel and transept, dating to the 14th century. The nave, aisles and porch are 15th century, with the tower dating from about 1500. The tower has angle buttresses, uncommon in Pembrokeshire, and in 1842 was noted as having turrets (pinnacles) and a spire. The pinnacles were removed in the 19th century and the spire in the 20th century. A number of other alterations, externally and internally, were made during the 19th century, including to roofing and windows.
In the chancel are the tombs of Sir Nicholas de Carew (died 1311, who built the Edwardian castle) and Sir John and Elizabeth Carew. There are memorials to members of the Allen and other leading families. The west window is an 1857 Crimea memorial.
Old Mortuary Chapel is a medieval Grade I listed building in St Mary's churchyard. The building has two storeys under a slate roof, is oriented east–west, and is built from limestone rubble. It is accessed by external steps. It has a vaulted undercroft.
There is an exterior monument to John Relly, an early Calvinist Methodist leader who died in 1777.
The undercroft dates from the 14th or 15th century, and may have been an ossiary. In 1625 the building was referred to as a schoolhouse, and was used for this purpose until 1872. The building may have been used as a mortuary chapel, and is known by that name. After 1872, the building, which has a large blocked-up window, was used as a committee room, store and as a residence, housing paupers as late as about 1840. Its current use is as a parish meeting room and Sunday School.
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.