These ivy-clad ruins, now sharing their field with grazing cattle and a modern farm complex, once served as the principal stronghold of the O’Melaghlin clan. Historical records from around 1548 mark this castle as their chief seat, though their tenure proved short-lived; by 1553, the Baron of Delvin and English forces from Athlone had wrested control of the fortress, adding another chapter to Ireland’s long history of territorial disputes.

What remains of Clonlonan Castle today is modest yet evocative. The western wall, rising approximately 8 metres despite centuries of neglect, forms the most substantial surviving element of the rectangular structure. Built with a mixture of large and small stones in what archaeologists diplomatically describe as “poor quality” masonry, the castle shows clear signs of having been robbed for building materials over the years, with its quoin stones notably absent. A single window opening at first floor level hints at the domestic arrangements within, whilst traces of a low foundation plinth and the ghost of a short return at the northwest corner help visitors imagine the castle’s original footprint.

The castle doesn’t stand entirely alone in its field; roughly 140 metres to the east-southeast, the remains of a horizontal water mill speak to the broader medieval landscape that once thrived here, whilst a bullaun stone, one of those mysterious boulder basins often associated with early Irish Christianity, lies about 190 metres to the east. Though the castle ruins are barely visible from aerial photography today, partly obscured by their mantle of ivy and the encroachment of time, they appeared clearly enough on the 1910 Ordnance Survey maps, depicted as a rectangular building with its long axis running north to south, already by then reduced to a shadow of its former defensive glory.