At Lissagarrymogh, on a gently east-facing slope in Tullaghanmore, County Roscommon, there is exactly that: a roughly circular earthwork with no identifiable entrance, its grassy banks still rising and its surrounding ditch still holding depth in places, yet offering no obvious point of passage in or out.

The site is a ringfort, the kind of enclosed farmstead that tens of thousands of Irish families occupied during the early medieval period, typically defined by one or more earthen banks and ditches enclosing a roughly circular area. Here the enclosure measures about 36 metres north to south and 32 metres east to west, and its defining bank, while overgrown and damaged in places by animal poaching, survives best along its western and northern arc, where the base widens to between six and eight and a half metres and the exterior face still stands over two metres high. Beyond the bank runs an outer fosse, a broad ditch averaging seven metres across at its top, which deepens noticeably toward the west, reaching 1.2 metres there compared with only a shallow trace along the south-eastern stretch. The interior itself is a grass-covered subcircular platform, quietly unassuming from a distance, the kind of slight rise in a field that might go unnoticed without some knowledge of what to look for.