McDermott's Castle

McDermott's Castle occupies Castle Island in the south-east corner of Lough Key, County Roscommon. The Mac Diarmada dynasty ruled Magh Luirg, or Moylurg, in northeast Connacht from the 10th century to the 16th, and a castle stood on the island from the 12th century. In 1184 the Annals of Loch Cé recorded that lightning burned "the very magnificent, kingly residence of the descendants of Máel Ruanaid": six or seven score of distinguished persons were destroyed, among them the wife of Mac Diarmada, his son's wife, Mac Maenaigh, chieftain of Cenél Builg, and the priest O'Maelbealtaine. Those not burned drowned in the entrance of the place, and none escaped alive but Conchobar mac Diarmata, with a very small number of his people.

A rebuilt castle on the island featured in the closing stage of the 1235 conquest of Connacht by Richard Mór de Burgh, 1st Baron of Connaught. The castle came under siege, first from a catapult mounted on a raft and then from fire ships, and Cormac MacDermott, king of Moylurg, was forced to surrender.

A poem addressed to Tomaltach an Einigh mac Diarmata, king of Moylurg from 1421 to 1458, tells of the Hag of Lough Key, who used — or abused — the hospitality of Cormac MacDermott, king from 1218 to 1244, by staying on the Rock for a full year, and who laid upon the McDermotts the obligation of perpetual hospitality.

The McDermotts lost the island in 1586, and Eochaidh Ó hÉoghusa, who lived from 1567 to 1617, wrote a poem lamenting the castle's emptiness.

By the early 19th century the castle was in ruin, until the architect John Nash was commissioned to redevelop it as a summer house or folly. He added wings on either side of the late-medieval tower house identified inside the main standing building, and a kitchen on the tower's eastern side; the tower's western wall keeps an arrow slot and medieval windows. Windows were inserted into the tower at the same time, and the enclosure wall was modified at the northern end of the island to give a view from the main new window.

Isaac Weld, writing in 1832, described as part of "the castle proper" two rooms, one above the other, each 36 by 22 feet with walls seven and a half feet thick, though it is not clear whether that refers to the original castle or the later work. The summer house Nash built burned down in the mid-20th century, leaving the island a partial ruin. The castle is a protected national monument.

Archaeological excavations on the island in 2019 concluded that it is essentially a multi-period fortification, its earliest elements dating to the early medieval era. An earlier enclosure wall two to three metres thick, pre-dating the standing enclosure wall, was excavated at a depth of a metre and a half, and thirteenth-century buildings were found on the northern side of the island above that earlier fortification, though they could not be connected to the standing wall. High-status Gaelic finds included silver pins, a gaming piece and large collections of butchered cattle, boar and sheep.

In 2014 the island and castle featured in an episode of the sitcom Moone Boy as the residence of the mysterious "Island Joe." The castle was put up for sale in 2018 for €80,000, but the sale was later withdrawn and the castle returned to private Irish ownership.