The majority of the remaining St Mary's Church dates from the 15th century with some features retained from the 13th century. There is believed to have been a church on the site since Norman times, and Gerald of Wales is counted as the earliest Rector of Tenby.
The 13th century chancel has a 'wagon' roof and the panelled ceiling has 75 bosses carved in a variety of designs including foliage, grotesques, fishes, a mermaid, and a green man, as well as the figure of Jesus surrounded by the four Apostles. St. Thomas' Chapel was added in the mid-15th Century, and the St. Nicholas Chapel was added c. 1485. The spire is also a 15th-century addition. Inside the church is a 15th-century font and a 15th-century bell, cast with the letters Sancta Anna.
The tower is positioned to one side of the chancel and dates from the late 13th century. The first floor served as a chapel, and still has a stone altar and piscina in place.
The church has two fonts, one dating from the 15th century and another late Gothic example from the 19th century.
The church contains several memorials, including the tombs of Thomas and John White, both Mayors of Tenby in the fifteenth century. Thomas White was famous for hiding a young Henry Tudor from King Richard III.
In the churchyard, 20 metres west of the church, are the remains of what is believed to be a late 15th-century choir school or college. The wall includes a pointed arched doorway.
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.