A megalithic tomb, likely dating from Ireland’s Neolithic period, was carefully marked on the original Ordnance Survey six-inch map drawn up in 1834. Yet when surveyors returned to update their maps in subsequent years, they found no trace of the ancient structure. Today, the site remains elusive; no stones, earthworks or other physical evidence can be found where the tomb once supposedly stood.

The only written record of this vanished monument comes from the OS Memoirs of 1834, which noted the site’s existence in Clonmany parish but frustratingly provided no details about its appearance, size or construction. Was it a portal tomb with its characteristic capstone? Perhaps a wedge tomb aligned with the setting sun? Or something else entirely? Without any description or surviving remains, archaeologists can only speculate. The tomb has been catalogued as ‘unclassified’ in official surveys, a designation that speaks to both its enigmatic nature and the broader challenges of documenting Ireland’s prehistoric heritage.

Several antiquarians and archaeologists have attempted to relocate the site over the years, including W.C. Borlase in 1897 and Seán Ó Nualláin in 1983, but their searches proved fruitless. The tomb’s disappearance could have multiple explanations; it may have been destroyed for building materials during the 19th century, a common fate for many ancient monuments, or perhaps the original surveyor made an error in recording its location. Whatever the truth, this phantom tomb serves as a reminder that Ireland’s archaeological landscape is constantly changing, with some mysteries buried not just in the ground, but in the gap between historical records and present-day reality.