It is believed that Saint Domangard or Donard founded a monastery in Maghera in the early christian period, c. 500 AD. He lived as a hermit on Slieve Donard, a nearby mountain that is named after him. There are no antiquities remaining from the early foundation but excavations in 1965 produced evidence of occupation around the tower during the Early Christian period. The medieval church situated behind the more modern church probably dates to the 12th century. It is much harder to date the round tower as there are no features such as windows or doors that normally help in dating round towers.
The tower, which is built from rough uncoursed granite field-stones similar to the tower at Castledermot, is believed to have fallen in the 18th century as a result of storm damage. All we see today is a 5.4 metre high stump with a large breech on the eastern side of the tower. This may represent the position of the doorway, suggesting a rather low entrance. The diameter of the tower at base level is 4.85 metres. The stones used in the building of the tower suggest a 10th century date but is not definite proof.
References:Trenčín Castle is relatively large renovated castle, towering on a steep limestone cliff directly above the city of Trenčín. It is a dominant feature not only of Trenčín, but also of the entire Považie region. The castle is a national monument.
History of the castle cliff dates back to the Roman Empire, what is proved by the inscription on the castle cliff proclaiming the victory of Roman legion against Germans in the year 179.
Today’s castle was probably built on the hill-fort. The first proven building on the hill was the Great Moravian rotunda from the 9th century and later there was a stone residential tower, which served to protect the Kingdom of Hungary and the western border. In the late 13th century the castle became a property of Palatine Matúš Csák, who became Mr. of Váh and Tatras.
Matúš Csák of Trenčín built a tower, still known as Matthew’s, which is a dominant determinant of the whole building.