Beneath its foundations lie the remains of Booterstown Castle, a 15th century fortification built by the Fitzwilliam family. The castle itself replaced an even earlier fortress that had been destroyed at the turn of the 15th century, prompting Philip Fitzwilliam to petition King Henry VI for funds to rebuild and fortify the site.

The castle’s history reads like a who’s who of Irish nobility and legal figures. In the early 1600s, it became home to Sir William Ryves, who served as Attorney General for Ireland. Following the Restoration in 1660, the Reyly family took up residence in the castle. The Ordnance Survey map of 1843 still marked the location as ‘Booterstown Cas’, acknowledging its castellated past even as the medieval structure had long since given way to more modern architecture.

Today, whilst no visible traces of the original castle remain above ground, the site hasn’t entirely forgotten its medieval origins. The current house is said to incorporate vaults from the 15th century castle into its structure; silent witnesses to centuries of Irish history hidden beneath the everyday facade of a Georgian residence. These underground chambers serve as the only physical link to the Fitzwilliams’ fortress and the strategic importance this spot once held, watching over the approaches to Dublin from the south.