Only when the lake level drops does it break the surface, a circle of material roughly five metres across, betraying the outline of a crannog. Crannogs are man-made island dwellings, typically constructed from timber, stone, peat, and brushwood, and used across Ireland from the Bronze Age well into the early medieval period as defensible homesteads set out over open water. This one, at Drumheel, has been confirmed not through any ground survey but through satellite photography alone.

Comparison of aerial imagery from Apple Maps around 2012, and from Google Earth on dates including May 2017, June 2018, and April 2020, each captured the island at moments when the water had receded just enough to reveal it. The bay it sits in measures roughly 550 metres on its longer north-northwest to south-southeast axis and around 440 metres across, with the crannog positioned near the outer, southern edge. Beyond that geometry, the site has not been visited or formally examined on the ground, which means the island's date of construction and its history of use remain entirely open questions. Lough Oughter itself is a complex, branching lake system in the drumlin belt of Cavan, and it already holds one well-known crannog site associated with the medieval O'Reilly dynasty, so the presence of another in its northern reaches is not entirely surprising, even if this one has gone largely unnoticed.