This one asks you to consider what has almost entirely disappeared. On a low east-west ridge at Coolbaun in County Galway, a circular earthwork that may once have enclosed a farmstead or defended a family's livestock has been reduced, by quarrying and agricultural use, to little more than a faint scarp along its north-western arc. A barn and a silo pit now occupy part of what would have been the interior. The enclosure survives more convincingly on paper than on the ground.

A rath is a ringfort, typically a circular area enclosed by one or more earthen banks and ditches, used in early medieval Ireland as a defended farmstead or high-status residence. They number in the tens of thousands across the island, and while many survive as prominent earthworks, others have been worn away over centuries of farming, construction, and land clearance. The Coolbaun example was recorded on the third edition of the Ordnance Survey six-inch map, published in 1945, where it appeared as a circular enclosure measuring roughly 33 metres on a north-east to south-west axis and about 28 metres north-west to south-east. That cartographic evidence, combined with its position on a ridge, typical of rath siting, is now among the stronger arguments for its original character. Without the map, almost nothing on the surface would prompt a second glance.