Though the castle itself is no longer visible at ground level, historical records paint a picture of what once stood here. The Down Survey of 1655-6, one of Ireland’s most important historical mapping projects, recorded a square keep with an extension on one side, suggesting this was once a substantial fortification commanding views across the north and east facing slopes that drop towards the river some 100 metres away.

The castle’s existence is further confirmed by the Ordnance Survey Letters, where O’Flanagan noted in 1928 that ‘an old castle stands in Castlesallagh townland’. This documentary evidence places the structure firmly within the historical record, even as the physical remains have vanished from sight. The name Castlesallagh itself preserves the memory of the fortification; the Irish ‘salach’ meaning dirty or muddy, possibly referring to the river valley’s marshy conditions.

Today, visitors to the townland will find little trace of the medieval stronghold that once controlled this strategic position above the Slaney. The castle likely served as one of many Anglo-Norman fortifications that dotted the Wicklow landscape, built to secure territory and protect settlements from the Irish clans who held sway in the nearby mountains. Its disappearance speaks to centuries of stone robbing for local building projects, a common fate for abandoned castles across Ireland where dressed stone was always a valuable commodity.