At its heart sits a bullaun stone, a type of carved rock basin that holds particular significance in Irish archaeology and folklore. This particular example features two distinct depressions carved into its surface: one measuring 34cm by 40cm with a depth of 23cm, and another much broader but shallower depression spanning 2 metres across but only 5cm deep. A carved channel connects to the first depression, designed to direct water into the basin.

The bullaun stone doesn't stand alone but forms part of a larger monument. It's surrounded by a cairn, a deliberately constructed mound of stones measuring 6 metres by 8.8 metres. This combination of bullaun and cairn is relatively unusual and suggests the site held considerable importance for the local community. Bullaun stones are found throughout Ireland and are often associated with early Christian sites, though many likely predate Christianity's arrival. They were typically used for grinding grain or herbs, though some may have held ritual significance, with their collected rainwater believed to possess healing properties.

The site was formally documented in the Archaeological Survey of County Donegal, compiled by Brian Lacey and his team in 1983, which catalogued field antiquities from the Mesolithic period through to the 17th century. The survey assigned it the reference number DG096-010008, with separate designations for the bullaun and cairn components. While the exact age and original purpose of Tobermurry remain uncertain, its careful construction and prominent placement in the landscape suggest it served as an important focal point for centuries of human activity in this part of Donegal.