True to its name, the castle sits on partially reclaimed grassland surrounded by poorly drained marshland, positioned near an ancient fording point that gave the townland its distinctive moniker. This location placed it strategically within a network of medieval strongholds; McElligott’s Castle lies 1.6 kilometres to the northeast in Arabela, whilst Ballycarty Castle stood 1.8 kilometres northwest.

The castle was reportedly built by the MacElligotts, a powerful family descended from the MacClowds of Scotland’s Isle of Skye who arrived in Ireland with Galfridus de Marisco, Justice of Ireland, and established themselves as major landowners in the area. When the Ordnance Survey documented the structure in 1841, it was already in ruins but still substantial, measuring approximately 6.9 metres north to south and 4.2 metres east to west internally, with walls an impressive 2.1 metres thick at the base. The surveyors noted two narrow limestone windows on the east side, one pointed and one angular, and described a doorway on the west side measuring 2.1 metres high and 1.2 metres wide. By 1871, the local parish priest reported it as “a substantial two storied square block” where cattle sheltered in the ground floor whilst grass grew luxuriantly on the upper level.

Today, only the northern half of Bealagrellagh Castle remains standing; the southern portion was demolished between 1924 and 1925 when locals used the stones for road building. What survives reveals fascinating construction details, including evidence of wicker centring used to support the stone vaulting during construction, visible as impressions in the mortar, and beam holes that once held timber supports. A large wall cupboard or aumbry can still be seen in the northeast corner of the ground floor, and broken window embrasures with segmental arches hint at the castle’s former defensive capabilities. Local folklore from 1938 remembered it as an Anglo-Norman castle with thick walls and stone staircases, though by then much of its grandeur had already been lost to time and practical necessity.