Built in the 13th century, this fortification sits within a rectangular enclosure, though time has not been entirely kind; the southwest wall has almost completely collapsed, leaving the structure in what archaeologists describe as “fair condition”. The castle’s defensive nature is evident in its design, with most windows consisting of narrow rectangular slits or single lights with flat heads, allowing defenders to observe and fire upon attackers whilst remaining protected.

The castle’s internal layout reveals fascinating details about medieval life and construction techniques. The original entrance, now robbed out, was positioned near the eastern corner of the southeast wall on the first floor, accessed by a wooden staircase supported by beams that slotted into the wall. Once inside, residents and defenders could move between floors via an intramural stairway built into the northern corner, connecting the first and second floors. All the floors were originally wooden, and whilst these have long since disappeared, the beam holes and structural evidence remain. The first floor featured larger windows, now also robbed out, which would have provided more light and ventilation to what were likely the main living quarters.

Archaeological surveys have revealed that Moylough Castle wasn’t an isolated stronghold; a church once stood approximately 110 metres to the east-southeast, suggesting this was part of a larger medieval settlement complex. The castle has been documented by various historians and archaeologists over the decades, including mentions in O’Flanagan’s work from 1927 and Waterman’s studies in the 1950s, with more recent comprehensive documentation appearing in the Archaeological Inventory of County Galway. Today, visitors can still observe the remaining walls from various angles, with the northeast wall’s slit window and the northwest wall providing particularly good examples of the original defensive architecture.