The heart-shaped island, roughly 280 metres north to south and 250 metres east to west, floats in Garadice Lough (formerly Lough Finvoy) and was previously known as Hog Island or Inis na dTorc. The castle’s history stretches back to at least 1257, when Con O’Rourke gave this fortified island to the O’Conors, though the O’Rourkes likely held onto it as their stronghold until 1418. That year marked a tragic turning point when Owen O’Rourke drowned whilst returning from visiting his dying father, Tiernan Mór, at the island castle. After this, the family relocated their power base to Drumahaire and north Leitrim.

By the seventeenth century, the castle had passed into the hands of Myles ‘the Slasher’ O’Reilly, whose main fortress stood on Crane Island at the southeast edge of the lake. The surviving structure, however, probably dates from sometime after the thirteenth century. What remains is a substantial rectangular building measuring about 19.5 metres east to west and 8 metres north to south internally. The western wall stands tallest at 2.7 metres high and 1.2 to 1.3 metres thick, though its corners have crumbled away. The other walls have been reduced to their foundation courses, and frustratingly for archaeologists, the walls are largely featureless; even the entrance location remains a mystery, with only some putlog holes visible in the western wall where scaffolding beams once supported medieval builders.

The castle sits within a D-shaped stone enclosure measuring 31 metres north to south and 26 metres east to west, with its straight eastern side just 4 metres from the castle walls. Like the castle itself, no entrance to this enclosure can be identified today. Adding to the site’s archaeological intrigue, a large cairn approximately 15 metres across and up to 2.5 metres high overlies the western and southwestern sections of the enclosure wall. Within this cairn, archaeologists have found a kiln measuring 2.1 metres in diameter and nearly a metre deep, which opens to the west, suggesting later activity on this already ancient site.