The one at Kerries, in County Kerry, does something more awkward and more interesting: it climbs. Built partly on flat improved ground and partly up the south-facing slope of a limestone outcrop called Rosky Hill, the enclosure takes on a shallow V-shaped profile, as though the people who built it were as interested in the geology of the place as in the practical business of enclosure.

Rosky Hill is what geologists call a Waulsortian mudmound, a type of ancient limestone reef formed from carbite-rich sediment in warm, shallow seas during the Carboniferous period, hundreds of millions of years before anyone thought to build a bank around it. The enclosure that wraps around its base and lower slope was described in detail by Michael Connolly in his 2008 UCC doctoral thesis on the prehistoric settlement of the Lee Valley near Tralee. Where the bank sits on the flat ground it is a mixed construction of earth and stone, up to 7.5 metres wide but worn down considerably, surviving to just 0.48 metres in external height. As it moves uphill onto the reef itself, the builders switched materials entirely, working in stone and incorporating the protruding bedrock directly into the structure. At the precise point where the enclosure begins its ascent, a small cairn sits centrally, 2.2 metres in diameter and just 0.22 metres high; modest in scale, but placed with apparent intention. The internal east-west measurement of the enclosure is 21.4 metres. Beyond the enclosure proper, further stretches of stone bank meander along the upper southern edge of the reef and down its eastern slope, the longest running to 7.5 metres, suggesting that the whole summit of the hill was subject to some form of organised use. A closely comparable complex lies just 385 metres to the west, which raises the possibility that Rosky Hill and its neighbour were understood, at some point in prehistory, as a pair.