Classified as a crannog, the site turns out on closer inspection to be something rather different: an overgrown cairn, roughly sixteen metres across, built from a matrix of small stones and charcoal. No evidence of the timber piles or wooden platforms typically associated with crannogs, the artificial or semi-artificial islands used as defended lake dwellings throughout early medieval Ireland, has ever been found here. Whatever this structure was, it was built with stone, not wood, and the presence of charcoal within the matrix hints at burning, though whether from construction, habitation, or destruction remains unclear.

Astrish Lough itself is modest in scale, measuring approximately 170 metres along its northwest to southeast axis and around 120 metres across. The cairn sits at its centre, giving it a quietly commanding position on the water despite its unassuming dimensions. The discrepancy between the crannog label and the actual physical evidence is not unusual in Irish archaeological recording; early classifications were often made on the basis of location alone, and a stone mound rising from a lake would naturally have attracted the designation. Whether the site represents a genuinely anomalous form of lake monument, a heavily modified natural feature, or something that has simply lost its wooden elements to time and decay, is a question the available evidence does not yet resolve.