Like so many Irish castles, Ballymoon has no recorded history, but on architectural grounds it must have been built c.1290-1310. The most likely builders were the Carew family, who evidently by this time had acquired the district (Idrone) from the Bigods, Earls of Norfolk. The castle - as striking as it is unusual - comprises a courtyard about 80 feet square, delimited by granite walls, 8 feet thick and 20 feet high. No doubt these walls had alures or wall-walks with crenellations, but these do not survive. Some flanking protection was provided by oblong latrine turrets projecting from three of its faces; the fourth curtain on the west has no such defence, though the gateway on this side, a plain arch with portcullis grooves, may origin ally have had a barbican in front.
The interior is now bare, but the walls' many embrasures, loops, fireplaces and doors bear witness to the former presence of two-storey ranges, some with cellars, that delimited the enclosure. The fine double-fireplace on the north belonged to the great hall, while such features as the cross loops with expanded terminals and "Caernarvon arches" allow us to date the castle to the turn of the thirteenth century. The castle may not have been in use for very long; indeed, some argue it was never finished.
Located 2 miles E of Bagenalstown in a field adjacent to the Fennagh road (L33). A small bridge gives access across a deep field ditch. NGR: S 738615. National Monument. Boots recommended.