At Lisnalee in County Monaghan, a drumlin top that once carried a ringfort now shows nothing at all to the aerial camera, only the smooth green of improved pasture, with no earthwork, no shadow, no trace of the circular bank and ditch that would once have marked this as an enclosed farmstead of early medieval Ireland.

A ringfort, known in Irish as a rath, was typically a domestic enclosure, a farmstead surrounded by one or more earthen banks, used throughout the early medieval period roughly between the fifth and twelfth centuries. They are among the most common archaeological monument types in Ireland, yet many have been levelled by centuries of agriculture. The Lisnalee site is recorded as a "Site of fort" on a revision of the 1834 Ordnance Survey six-inch map, the revision itself dated 1858, which suggests that by the mid-nineteenth century the fort was already gone or largely gone, reduced in the surveyors' language to a memory of a feature rather than the feature itself. That the mapmakers noted it at all is something; it fixes the location and confirms that local knowledge of it persisted at least into the Victorian period.

The drumlin setting is worth pausing on. Drumlins are the low, smooth, egg-shaped hills formed from glacial debris that give much of County Monaghan its distinctive rolling character. Positioning a ringfort on a drumlin summit would have offered good visibility across the surrounding landscape, a practical advantage for an early medieval farming family keeping watch over livestock and land. Today, that elevated position survives, but the monument it once carried does not.