Most visitors to the Irish countryside walk past collapsed stonework without giving it a second thought, but what remains here is the ghost of a cashel, a type of ringfort built from drystone rather than earthen banks, its circular outline still readable in the landscape even as the wall that once defined it has largely fallen in on itself.

The cashel measures approximately 40 metres in diameter, and its enclosing wall survives in recognisable form only along the arc running from the south-west, through the west, and around to the north. For the rest of the circuit, the boundary has been reduced to a natural-looking scarp in the ground, the kind of subtle edge that might pass unnoticed unless you already know to look for it. Two later field banks cross the monument at the south-west and north-west, cutting through the remains in the way that centuries of agricultural reorganisation tend to do. Most intriguing is a small circular depression, roughly two metres across, tucked into the wall on the north-north-west side. It may be the surviving trace of a subsidiary hut, perhaps a structure that once stood within or against the enclosure wall. A cashel in good condition typically presents a thick, mortarless stone wall enclosing a domestic or high-status settlement; what survives at Tonacooleen is the most reduced version of that picture, the outline without much of the substance. A clochán burial ground is recorded in association with the site, adding a further layer to whatever community once made use of this hilltop.