At Castleroan in County Offaly, a ringfort, the type of circular earthwork enclosure built in early medieval Ireland as a defended farmstead, once occupied land that is now entirely given over to a quarry. Nothing of it survives at ground level, and in practical terms the site has ceased to exist as a physical place.

What we know of it comes largely from the Ordnance Survey's six-inch mapping of 1840, where it appears as a clearly defined circular enclosure. That survey, carried out with considerable care across the entire island, captured the outlines of thousands of such features at a moment before intensive agriculture, drainage schemes, and industrial extraction had erased so many of them. The Castleroan ringfort was among those that did not survive the following century and a half intact. Quarrying, which removes not just the surface but the ground itself, is among the most absolute forms of destruction a site can suffer; there is no question of buried deposits quietly persisting beneath disturbed soil.