On the eastern side of Ringarogy Island in the estuary of the Illen River in County Cork, a passage tomb, locally known simply as the Lag, sits so low on a small rocky eminence that the sea swallows almost all of it twice a day. What remains visible above the high-water mark amounts to the tops of two upright stones, draped in seaweed, offering little hint to a passing boat that anything of archaeological consequence lies beneath the surface.

Passage tombs are megalithic monuments, typically Neolithic in origin, in which a stone-lined corridor or gallery leads to a burial chamber, the whole originally covered by a earthen or stone mound. The Lag preserves a gallery three metres long and one metre wide, aligned roughly east to west, with three sidestones on each side. At the eastern end, a tall jamb-like stone standing 1.1 metres high, alongside a smaller orthostat, suggests the entrance was once deliberately elaborated, perhaps framed in a way that marked the threshold between outside and inside. A substantial backstone closes the western end. Four prostrate slabs to the east of the entrance and two more to the south are thought to be displaced roofing elements, the cap-stones that once sealed the gallery now tumbled and scattered. Three kerbstones, the stones that would originally have edged the covering mound, survive in place roughly two metres north of the gallery, with three further possible examples identifiable to the northwest. The mound itself has been largely destroyed by centuries of tidal action, which accounts for the tomb's present condition as much as any human interference. The work of Shee Twohig, published in 1995, provides the detailed account from which this picture is drawn.

Access to Ringarogy Island depends entirely on tidal timing, and the tomb itself is only meaningfully visible at low water. Anyone wanting to see the gallery stones and surviving kerbstones would need to plan accordingly, bearing in mind that the seaweed covering makes the stones difficult to distinguish at a glance from the surrounding rock.