Nendrum Monastery tower

Nendrum Monastery tower

Nendrum Monastery ruins

Nendrum Monastery ruins

Nendrum Monastery was a Christian monastery on Mahee Island in Strangford Lough, County Down, Northern Ireland. Medieval records say it was founded in the 5th century, but this is uncertain. The monastery came to an end at some time between 974 and 1178, but its church served a parish until the site was abandoned in the 15th century. Some remains of the monastery can still be seen.


The island monastery of Nendrum was traditionally founded in the 5th century by Mochaoi, after whom Mahee Island is named, although a later date for the foundation has been suggested. Mo Chaoi, like the name of many Irish saints, is a pet-name. His proper name was Caolán and according to tradition he was appointed by St. Patrick. However, dendrochronology has dated a tide mill on the island to the year 619, making this the oldest excavated tide mill anywhere in the world. The monastic site included orchards, gardens, pastures, arable fields, and a guest-house. In his Ecclesiastical Antiquities of Down, Connor, and Dromore, William Reeves notes that several annals record the death of St Mochaoi of Nendrum at a variety of dates between 490 and 497. He considers that Nendrum was early chosen as the seat of a bishop, quoting the Annals of Tigernach and the Annals of Ulster, both of which describe Cronan (died c. 640) as "bishop of Nendrum".

There are references to Nendrum in various sources, such as the Annals of the Four Masters, between the 7th century and the year 974, when the Four Masters record that "Sedna Ua Demain, Abbot of Nendrum, was consumed in his own house". This is read as meaning that Sedna was burnt, perhaps during a Viking raid, and is the last heard of Nendrum in the annals. Reeves says "Probably it was pillaged and demolished soon after by the Danes, whose ships were continually floating in Strangford Lough. When the name next occurs, it is as belonging to property of the see of Down, with which John de Courcy, in 1178, takes the liberty of making it over to the monks of an English abbey. It would seem, however, that long ere this it held some tributary relation to the see of Down..."

The English monks were Benedictines and founded a small cell on Mahee Island. However, in 1306 Nendrum was recorded as a parish church, and during the 15th century it was abandoned for a new site at the village of Tullynakill. The location of Nendrum was then lost until it was rediscovered in 1844 by William Reeves, who visited the island searching for the church recorded in 1306 and recognized the remains of a round tower.


Since being excavated by H. C. Lawlor between 1922 and 1924, with the resulting finds now kept in the Ulster Museum, the site has been much restored. The rectangular building yielded about 30 slate tablets bearing Celtic designs. These 'trial-pieces' are now in the Ulster Museum along with a bell and a stone with an inscription in runes also from the site. Parts of the site were excavated later, by A. C. Thomas in 1954, by D. Waterman in the 1960s and by N. Brannon in 1979 and 1982. Lawlor's work was the first extensive excavation of such a large ecclesiastical site, and his technique has been criticized by modern standards, but one of the reasons for Nendrum's importance to archaeologists is that it is still the only major site of its kind which has been the subject of published excavation reports.

The principal monastic remains which can now be seen are three concentric cashels (enclosures) of dry stone walling, but these were substantially rebuilt by Lawlor in the 1920s. The central cashel has the round tower remains, a ruined church with a sun-dial, and a graveyard. The second cashel contains what is called a 'monastic school' or workshop and other burials. The canonical sundial now seen at one corner of the ruined church was reconstructed from fragments found during the excavation of the site in 1924 and has been dated to about the year 900. One of only a few early medieval sun-dials known to exist, it takes the form of a vertical stone pillar, 190 cm high, 40 cm wide and 15 cm thick, with the dial and gnomon on one face at the top. However, because of the nature of the reconstruction, the original height of the pillar is conjectural. An annual service is now held by at least one local parish at the monastery, on Palm Sunday.

The round tower Nendrum is one of only three towers in county Down, sadly all three are incomplete. We know very little about this monument as unfortunately the monastic site at Nendrum was 'lost' for centuries. The monastery was abandoned in the 15th century and forgotten about until 1845, when the Irish Antiquarian and ecclesiastical historian William Reeves identified the site as the monastic site Oendruim mentioned in earlier sources. Reeves, who was searching for churches listed in the papal taxation list of 1306 was bought up to see a 'lime kiln' at the site, but immediately identified it as the stump of a round tower. Reeves later became Bishop of Down, Connor and Dromore from 1886 till his death in 1892. The site remained overgrown until H.C. Lawlor carried out excavation and restoration work between 1922 and 1924. Today the tower stands at about 4.25 metres high. There are no features present except for the foundation or offset that is now clearly visible, see image below. The other round towers in County Down are at Drumbo and Maghera. Northern Irelands finest example is probably the complete tower on Devenish Island, Lower Lough Erne County Fermanagh.


Mahee Island is within Strangford Lough, a body of water which has been designated as an Area of Outstanding Natural Beauty. The island is approached by narrow roads and causeways leading from the A22 road south of Comber, which is the road to Downpatrick. A cottage was built on the island in the early 20th century and is now used as a visitor centre. The island is open daily from 10 am to 6 pm between Easter and 30 September, and from 12 pm to 4 pm on Sundays from October to Easter. Free parking is available. The visitor centre has toilet facilities. The ground is mainly grass and a wheelchair user would need assistance.


Location : Nendrum Monastic Site, Mahee Island Ringneill Road, Comber, County Down BT23 6EP

Transport: Bangor (NI Rail) then bus + taxi. Bus Routes : No Service.

Opening Times : Daily, Easter through September 10:00 to 18:00

Tickets : Free

Tel: 028 9082 3207