First recorded on the 1845-7 Ordnance Survey map, this enigmatic feature sat on gently sloping pastureland just west of Croaghan Hill, roughly two kilometres east of a cruciform passage tomb in nearby Kilmonaster Middle. When antiquarian Thomas Fagan visited the site in 1846, he found the remains of what appeared to be a stone structure measuring about 6.7 metres long and between 0.6 and 1.2 metres wide, oriented roughly north to south. The monument consisted of flat stones, some still standing up to 0.9 metres high, enclosing the space, whilst a substantial flat stone at the southern end, measuring approximately 2.15 metres by 1.2 metres, seemed to cover what might have been a burial chamber.

By 1870, however, this intriguing monument had completely vanished from the landscape, as noted in the Ordnance Survey Name Book of 1903-4. No trace remained of what Fagan had documented just a quarter of a century earlier; the stones that once marked this ancient site had been removed, repurposed, or simply lost to time. The speed of its disappearance speaks to the vulnerability of Ireland’s archaeological heritage during the 19th century, when agricultural improvements and land clearance often took precedence over preservation.

Whilst the Giant’s Grave may have been a megalithic tomb, possibly dating back thousands of years to Ireland’s Neolithic period, the evidence is frustratingly incomplete. The description suggests characteristics common to portal tombs or court tombs found elsewhere in Donegal, but without proper excavation or more detailed documentation, its true nature remains a mystery. Today, the site exists only in historical records and survey notes, a ghost monument that reminds us how much of Ireland’s ancient past has been irretrievably lost.