At Derryroe in County Cork, a cashel, a type of ringfort built from dry-stone walling rather than earthen banks, once occupied a roughly circular footprint of around thirty metres across. Today there is nothing to see. The ground gives no hint that anything was ever there, and the site survives only because cartographers recorded it and one researcher thought to note it down before even that faint impression was gone.

The 1842 Ordnance Survey six-inch map shows the enclosure as a circular feature, which is how most cashels appear from above: a ring of stone wall enclosing a domestic or defensive space, a form of settlement common across Ireland from the early medieval period. By the time P. J. Hartnett visited in 1939 and recorded his findings, the structure measured approximately 30.5 metres in diameter and was already described as levelled. That figure, committed to print in 1939, is now among the few concrete facts that survive. The stone is gone, the wall line is gone, and any archaeology that once lay within the enclosure may well have gone with it.

What is quietly interesting about a site like this is how it illustrates the way the archaeological record works. The cashel at Derryroe is not lost in any dramatic sense; it was documented, mapped, and catalogued. It simply no longer exists as a physical thing in the landscape, only as a coordinate and a diameter in a mid-Cork inventory. The 1842 map becomes, in effect, the monument itself.