A tumulus can be found close to the Grianán of Aileach in County Donegal. It has been suggested by historians such as George Petrie, who surveyed the site in the early 19th century, that the tumulus may predate the ringfort of Aileach by many centuries possibly to the neolithic age. Surrounding stones were laid horizontally, and converged towards the centre. the mound had been excavated in Petrie's time, but nothing explaining its meaning was discovered. It was subsequently destroyed, but its former position is marked by a heap of broken stones. Similar mounds can be found at The Hill of Tara and there are several prominent tumuli at Brú na Bóinne in County Meath.