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:Visby Cathedral (also known as St. Mary’s Church) is the only survived medieval church in Visby. It was originally built for German merchants and inaugurated in 1225. Around the year 1350 the church was enlarged and converted into a basilica. The two-storey magazine was also added then above the nave as a warehouse for merchants.
Following the Reformation, the church was transformed into a parish church for the town of Visby. All other churches were abandoned. Shortly after the Reformation, in 1572, Gotland was made into its own Diocese, and the church designated its cathedral.
There is not much left of the original interior. The font is made of local red marble in the 13th century. The pulpit was made in Lübeck in 1684. There are 400 graves under the church floor.