Mcdermott's castle - the irish island castle

What is McDermott’s Castle?

McDermott’s Castle is a castle and National Monument in County Roscommon, Ireland.

Where is McDermott’s Castle?

McDermott’s Castle is found on Castle Island, an area of 0.23ha (0.57 ac), in the southeast corner of Lough Key.

McDermott’s Castle is located in County Roscommon, on Lough Key, 3km northeast from Boyle.

Lough Key is approximately 10km in diameter and has over 30 islands scattered around its chilly waters.

One of these islands is appropriately named “Castle Island”, and you will find McDermott’s Castle ruins.

History of  McDermott’s Castle

From the 10th century to the 16th century, the Mac Diarmada was the ruling dynasty in Magh Luirg (Moylurg, northeast Connacht). This island was home to a castle since the 12th century. In 1184, the  Annals of Loch Ce reported that a lightning bolt set off a fire.

The Rock of Loch-Ce was burned by lightning, i.e. the very magnificent, kingly residence of the descendants of Mael Ruanaid where neither goods nor people of all that were there found protection; where six score, or seven score, of distinguished persons were destroyed, along with fifteen men of the race of kings and chieftains, with the wife of Mac Diarmada, i.e. the daughter of O hEidhin, and his son’s wife, i.e. the daughter of Domhnall O’Conchobhair, and the daughter of O Dubhda, and the son of Donnchadh O’Maelbhrenuinn, and the son of Donn O’Mannachain, and the two daughters of O’Mannachain, and Mac Maenaigh, the chieftain of Cenel-Builg, and the priest O’Maelbealtaine, and Gillachiarain O Connachtain, (i.e. a son of chastity and lamp of piety), and a countless destruction besides of good men; and every one of them who was not burned was drowned in this tumultuous consternation, in the entrance of the place; so that there escaped not alive there from but Conchobar mac Diarmata with a very small number of the multitude of his people.

In Richard Mor de Burgh’s 1235 conquest, Connacht, 1st Baron de Connaught featured a rebuilt castle in the final section. First, a catapult mounted on a raft was used to take the Castle down, then fireships were used to attack it. Cormac MacDermott was made King of Moylurg.

A poem addressed by Tomaltach and Einigh mac Diarmata, King of Moylurg (1421-58), tells the tale of the Hag at Lough Key, who used (or abused?) Cormac MacDermott (king 1218-44) hospitality. He stayed on the Rock for a full calendar year. He imposed upon the McDermotts a perpetual obligation to be their host.

Px lough key castle island
By se keenan – own work, cc by-sa 4. 0, https://commons. Wikimedia. Org/w/index. Php? Curid=51773548

In 1586, the island was lost to the McDermotts. Eochaidh O’hEoghusa wrote an indignant poem about the Castle’s demise.

The episode of the sitcom Moone Boy featured the Castle and island as the home of the mysterious “Island Joe” in 2014.

The Castle was up for sale in 2018 for EUR80,000. The offer was withdrawn later, and the Castle was returned to Irish ownership.

2016 saw licensed excavations at Rockingham’s moated site. This was suggested by some interpretations of Annals of Connacht to be remnants of a medieval marketplace. This location may have been the landward component of the fortified Rock of Lough Key.

A large enclosure was discovered around the moated site that dates back to the 13th century. It covered an early medieval ringfort ditch. The moated site was also found to have a large grain drying kiln with an indeterminate date. The site was identified by artefacts that clearly placed the date of the moated site in the medieval period.

The island was also the site of archaeological excavations in 2019. Archaeological excavations revealed that the island is an essentially multi-period fortification. The earliest elements date back to the early medieval era.

At a depth of one meter and a quarter, an earlier enclosure wall measuring two to three meters thick was found. The northern side of the island was excavated above the earlier fortification. Still, they were not connected to the standing enclosure walls.

There were many high-status Gaelic artefacts found, including silver pins and a gaming piece. Also, large amounts of butchered sheep, boar, cattle and sheep were found. Archaeology Magazine featured the research on the island.

Px castle island in lough key forest park
By apiechorowska – own work, cc by-sa 4. 0, https://commons. Wikimedia. Org/w/index. Php? Curid=43161065


Isaac Weld wrote in 1832 that two rooms were part of “the castle itself”, and each measured 36×22 feet (11x7m) with walls 7 1/2ft (2.2m). It is unclear whether this refers either to the original Castle or to the later construction.

At least three periods are responsible for the standing remains found on the island. The island’s enclosure wall is the oldest standing remnant. O’Conor et al. O’Conor et al. argued that the enclosure walls are likely of medieval construction.

However, the wall has not been dated, and excavations by Finan & Schryver were unable to connect the enclosure wall with their excavations. O’Conor et al. O’Conor et al. identified a medieval tower house in the interior of the main building. The tower house’s western wall is home to an arrow slot as well as medieval windows.

John Nash, an architect, added the additions to the tower on either side and the kitchen on the east side of this tower house in the early 19th century. Windows were then inserted into the medieval tower house. To allow a view through the main window in the tower, the enclosure wall was moved to the northern end. It was first built as a summer home and destroyed during the Second World War.

Few castles are as unique as McDermott’s Castle in Ireland.

Mcdermotts castle ireland

As you can see from the photo above, it’s literally sitting on a tiny green island in the middle of a lake.

McDermott Castle receives far less attention than Blarney Castle and the most haunted castles in Ireland, but it is still worth visiting.

The guide below will tell you everything you need to know about this fairytale-like Castle.

A story of tragedy

According to local legend, Una, a girl from McDermott’s daughter, fell in love with a man of lower class.

Una’s father insisted that she leave the island with her in the hope of preventing a budding relationship.

Una’s father did not know that her boyfriend started swimming across Lough Key to reach the Castle. The tragedy struck when the boy drowned during one of these crossings.

Una, along with her partner, died of grief. They have been buried under two intertwined trees since then.

How to get to McDermott Castle

Many tour companies offer tours to McDermott Castle and Castle Island.

Lough Key Forest Park is a must-see for anyone visiting the region. The park is home to approximately 800 hectares worth of beautiful, scenic woods and parkland that includes a lake and a few wooded islands.

Take some time to explore the park.

  • Take a look at the observation tower
  • Take a look at the wishing seat
  • You can walk through the underground tunnels.
  • Stroll along the Trinity Bridge
  • Take a look around the Bog Garden
  • Take in some of the histories of the area at the visitor centre and learn about the rich history of the area

Further Reading


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