This small tower house, which overlooks a lake to the south, now consists of little more than fragments of its southern and western walls. The southern wall stretches about 7.5 metres in length and stands 2 metres high, whilst a portion of the western wall reaches 3 metres in height. Built from rubble stone without any dressed masonry or defensive base batter, the castle originally formed a compact rectangular structure measuring approximately 10 by 9 metres. The hillock itself shows signs of deliberate landscaping, with scarped sides and traces of a defensive ditch on its eastern edge, though no evidence remains of an outer bawn wall that might have enclosed a courtyard.

The castle appears on the 1837 Ordnance Survey Fair Plan maps, where it’s marked as ‘Mulchan’s Castle in ruins’, suggesting it had already fallen into disrepair by the early 19th century. Curiously, it doesn’t feature on either the Down Survey parish map of Killulagh or the Barony map of Delvin from the 1650s, raising questions about when exactly it was built or whether it had already lost its significance by that time. The medieval parish church of Killulagh lies just 620 metres to the west, indicating this area held religious and strategic importance for the local community.

Historical records show that by 1641, the lands of Mulchanstown belonged to Sir Thomas Nugent, identified in the Down Survey as an ‘Irish Papist’. This designation places the castle firmly within the context of Ireland’s religious and political divisions during the 17th century, when Catholic landowners faced increasing pressure from Protestant authorities. Today, whilst the castle’s walls have been extensively robbed for building materials and grass covers much of the remaining foundations, the site still commands an impressive view across the surrounding wetlands, much as it would have done during its active years as a defensive stronghold.