What was once a substantial stone fort has been reduced, by time and weather, to a spread of large foundation stones, their base courses still visible at a maximum height of half a metre. The wall itself, where it can be traced, runs between three and four metres wide, suggesting something originally quite solid. A later drystone wall, the kind built by stacking unmortered stone, sits on top of the older revetted spread in places, a quiet reminder that the site was reused or at least maintained long after its original purpose was forgotten.

The enclosure is subcircular in plan, measuring roughly 31 metres east to west and 27.5 metres north to south on the interior, with the outer dimensions running to about 37 metres by 35 metres. A single entrance, just 1.4 metres wide, passes through the drystone wall on the northern side; no other opening has been identified. The interior is now grass and scrub, with trees growing at the centre, which gives it a quietly overgrown atmosphere rather than the open, surveyed look of more visited sites. Its position on the rock outcrop, modest as that outcrop is in such flat, drumlin-scattered terrain, would have made it a naturally defensible and visually prominent location in the surrounding low-lying ground. Details of this kind of stone ringfort, an enclosed area defined by a substantial rubble or drystone boundary wall, appear throughout Ireland, though many remain as poorly understood as this one. The site at Tully is recorded in Michael J. Moore's Archaeological Inventory of County Leitrim, published in 2003.