Though classified as a holy well, there's no actual well or spring here; instead, visitors will find a bullaun stone, a rock with carved depressions that collect rainwater, surrounded by a cairn measuring 6 by 8.8 metres. The bullaun features two basin-like depressions of varying sizes, with the larger one spanning 2 metres across, and a carved channel that directs water into the smaller, deeper basin.

This site forms part of a sacred landscape that has drawn pilgrims for centuries. Writing in 1936, the scholar Ó Muirgheasa documented three holy wells in Kilcar: Tobar Charthach (St. Carthach's Well), Tobar Chonaill (St. Conall Caol's Well), and Tobar Mhuire (the Blessed Virgin's Well). Even in his time, crowds of pilgrims were still performing the traditional station or turus, a ritual journey that begins in the ruins of St. Carthach's church, continues with three circuits around each of the holy wells, and concludes at what's known as 'the altar' back in the old church.

The persistence of these pilgrimages speaks to the enduring spiritual significance of these sites in County Donegal. While the church may be in ruins and the 'holy well' may lack flowing water, the carved stone and its surrounding cairn continue to serve as tangible links to centuries of religious practice and folk tradition in this corner of Ireland.