McDermott's Castle

McDermott’s Castle is situated on Castle Island within Lough Key, in the municipality of Rockingham Demesne, County Roscommon, Ireland. It was established by the Gaelic Mac Diarmada clan, who ruled the Magh Luirg region from the 10th century onward and used the castle as their royal residence.

The site has a recorded history stretching back at least to the 12th century. In 1184, the castle was struck by lightning, resulting in a catastrophic fire that caused the deaths of many nobles, including members of the Mac Diarmada family. This event is noted in the medieval Irish chronicle, the Annals of Loch Cé. By the early 13th century, the strategic importance of the castle was highlighted during the Anglo-Norman expansion into Connacht. In 1235, Richard Mór de Burgh led a siege against the fortress, employing innovative tactics such as raft-mounted catapults and fire ships. Despite resistance, Cormac MacDermott, the reigning King of Moylurg, ultimately surrendered the stronghold.

After this period of occupation, the Mac Diarmada clan managed to regain control of the castle, which remained an important seat through the 15th century. A notable cultural tradition associated with the site stems from a local legend about the Hag of Lough Key, who is said to have resided at the castle for a year. According to this tale, her presence imposed a lasting obligation of hospitality upon the Mac Diarmada family, reflecting the intertwined relationship between the clan and their ancestral stronghold.

By the late 16th century, specifically in 1586, the Mac Diarmada lost possession of the castle and the island. Over the following centuries, the structure gradually fell into ruin. In the early 1800s, the renowned architect John Nash undertook a redevelopment, transforming the remnants into a summer house or folly. This structure incorporated some medieval elements but was largely an imaginative redesign meant for leisure rather than defense. Unfortunately, Nash’s summer house was destroyed by fire in the mid-20th century.

In recent times, archaeological investigations conducted in 2019 revealed multiple phases of construction and occupation on Castle Island. These discoveries included fortifications from various periods, medieval buildings dating to the 13th century, as well as high-status Gaelic objects such as silver pins and gaming pieces, shedding light on the castle’s prolonged significance. McDermott’s Castle has also appeared in modern media and remains privately owned in Ireland.