Running along its eastern end is a 23-metre embanked structure that looks, from the air, very much like a raised causeway or formal entrance, though whether that is what it actually is remains an open question. The banks on either side are parallel, their outer faces rising to around 1.3 metres, and the interior has a distinctive U-shaped profile roughly 4.5 metres wide. The northern bank works with existing bedrock outcrops, supplementing them with earth and stone; the southern side does much the same in reverse. The structure leads directly from level ground at the eastern end of the spur to the wall of a central enclosure, suggesting deliberate design, but its precise function has never been confirmed.

The spur itself sits at the centre of an unusually layered archaeological landscape. Early maps record the surrounding low-lying land as marshy, which would have made the limestone ridge appear almost island-like, the only dry approach coming from the east, precisely where the causeway-like structure begins. That geography was almost certainly not incidental to whoever shaped this place. The reef, composed of Carboniferous limestone, carries remarkably rich fossil evidence and reaches a maximum height of 32 metres above sea level. Alongside the causeway, the site includes ramparts, smaller enclosures, a hilltop enclosure interpreted as a possible henge (a roughly circular monument, usually defined by a bank and ditch, associated with prehistoric ceremonial activity), quarry ditches, and cairns. The full complexity of the site came to light in 1999, when archaeologist Michael Connolly carried out trial excavations ahead of the construction of a new link road, the N22 between Ballycarty Cross and the Killarney road, with work commissioned by the Office of Public Works. The spur's commanding position overlooking two fording-points on the River Lee and the main passes through both flanking mountain ranges suggests it was a place of some strategic or ceremonial significance, though the archaeology has not yet been examined in enough detail to say which, or whether both applied at once.