Whilst the current structure dates to the 18th century, it sits atop something far more intriguing: massive foundations and vaults that likely belonged to a 17th-century castle. This earlier fortification, now hidden beneath the Georgian elegance above, hints at Ashgrove's strategic importance during Ireland's turbulent plantation period.

The site reveals more secrets upon closer inspection. West of the house, remnants of what appears to be the original bawn wall still stand, featuring a distinctive row of arched recesses flanked by engaged masonry columns. These defensive walls, which would have enclosed and protected the castle complex, measure roughly 0.6 metres thick; a testament to the serious fortifications required during those uncertain times. The survival of these architectural features offers a rare glimpse into how Irish castle sites evolved and adapted through the centuries.

Archaeological investigations by Davies in 1948 first brought attention to these hidden remnants, recognising their significance in understanding the site's complex history. The transformation from defensive stronghold to Georgian residence reflects broader changes in Irish society, as the need for fortified homes gave way to more comfortable country houses. Today, Ashgrove stands as a physical timeline, its stones telling the story of Ireland's transition from medieval warfare to modern domesticity.