The site’s story begins in 1447 when Anne Eustace took possession of Clongowes Wood Castle, a tower house that would meet a violent end nearly two centuries later when it was blown up during the Confederate Wars in 1641. For over 350 years, the exact location of this lost castle remained a mystery, until archaeological excavations at the college between 2002 and 2003 revealed that students had been walking through its remains all along.

The excavations uncovered evidence of a 17th century fortified house built into the very fabric of the school building. The structure that emerged from the archaeological assessment was a formidable T-shaped building, complete with flanking towers at either end of its main façade and surrounded by a defensive fosse; a water-filled ditch designed to keep attackers at bay. The building’s unusually thick internal walls suggest that parts of Anne Eustace’s original 15th century tower house may have been incorporated into the later fortification, creating a palimpsest of defensive architecture spanning two centuries.

What makes Clongoweswood particularly fascinating is how each era left its mark on the building. After its days as a fortified house ended, the 18th century brought elegant neo-classical interiors that transformed the militant structure into something more refined, whilst the Victorian era added a Gothic Revival extension to the rear. Today’s school building is essentially a timeline in stone and mortar, where medieval defensive walls support Georgian elegance, and where students study in rooms that once prepared for siege warfare.