At Windgates in County Kildare, there is a ringfort that you cannot see by standing in a field and looking around. No earthen bank rises from the ground, no ditch interrupts the grass, no obvious feature announces itself to a passing walker. What exists instead is a ghost, a circular mark pressed into a crop, readable only from the air.

Ringforts are among the most common archaeological monument types in Ireland, typically dating from the early medieval period, roughly the fifth to twelfth centuries. They were enclosed farmsteads, their residents protected by one or more banks and ditches, and they survive in their thousands across the country, some well-preserved, others reduced to faint humps. The example at Windgates belongs to a more elusive category: a cropmark site. When a buried feature such as a filled-in ditch lies beneath cultivated ground, the soil above it retains moisture differently from the surrounding earth. In dry summers, this difference shows up as a variation in the colour or height of growing crops, tracing the outline of whatever lies beneath. Here, aerial photography captured on 28 June 2018 via Google Earth revealed a circular enclosure of approximately 39 metres in diameter, the buried remains of what is almost certainly one of those early medieval farmsteads, invisible at ground level but legible from above as a ring drawn faintly in the landscape.