Located just south-southwest of the mountain’s trigonometrical station, this small spring has drawn pilgrims and locals for generations, all seeking the healing waters said to cure eye ailments. The well’s reputation for curative properties stems from local tradition, which holds that the waters were blessed either by one of the area’s holy bishops or, according to some accounts, by St Patrick himself during his legendary forty-day sojourn in the region.

The well’s connection to St Patrick adds another layer to its significance in local folklore. As the story goes, the saint blessed these waters whilst overseeing the construction of Domhnach Mór Muighe Tochair, a great church in the locality. This association dates back centuries, with Dr. O’Donovan documenting the site and its traditions as early as August 1835, noting how peasantry from across the region would make the arduous climb to apply the sacred waters to their eyes.

The site was catalogued as number 98 in Ó Muirgheasa’s 1936 survey of holy wells, and later included in the Archaeological Survey of County Donegal, which documented field antiquities from the Mesolithic period through to the 17th century. Despite its remote location atop one of Donegal’s notable peaks, Tobar na Súl continues to represent an enduring example of Ireland’s ritual landscape, where natural springs became focal points for healing traditions and religious devotion that persist into modern times.