According to the Ordnance Survey Letters from 2002, this was no ordinary fortification; local tradition holds that it belonged to one of the twelve sons of Horus (Pierce) Birmingham, a family who apparently dominated this region with their network of castles. Today, all that remains is a circular mound roughly 10 metres across at its base, tapering to about 2 metres at the top and standing nearly 3 metres high, with fragments of mortared stone occasionally breaking through its earthen covering.

The site tells an intriguing story about medieval defensive architecture and its eventual decline. Unlike typical castle locations that favoured elevated, easily defensible positions, Balrinnet Castle was built on low-lying ground in open countryside, suggesting its builders may have prioritised other considerations such as access to water, trade routes, or agricultural lands. The remains appear to be those of a tower house, a type of fortified residence popular amongst the Irish gentry from the 14th to 17th centuries, though the exact date of construction remains unclear.

The castle ruins don’t stand in isolation; they’re part of a broader medieval landscape that includes traces of an old field system and what appears to be a hollow-way, a sunken track worn down by centuries of use. These features paint a picture of a once-thriving medieval settlement, where the Birmingham family and their tenants would have worked the land and travelled these ancient paths. While the castle itself has been reduced to little more than a hill of rubble and earth, its presence continues to mark this corner of Kildare as a place where medieval Ireland’s complex tapestry of local lordships once held sway.