This one in Ballyelan, County Limerick, does the opposite: it has been almost entirely erased, and what remains is little more than a faint crease in a field. A shallow depression, roughly two metres wide and just ten centimetres deep, traces a rough circle across the pasture, enclosing an area of about twenty-two metres north to south and twenty-three metres east to west. Blink, or visit in the wrong light, and you will see nothing at all.

A rath is an earthen ringfort, the kind of enclosed farmstead built across Ireland from the early medieval period onwards, typically consisting of a circular bank and ditch surrounding a domestic area. Thousands survive in various states across the country. This one in Ballyelan was still visible enough in 1923 to be recorded on the Ordnance Survey six-inch map of that year, depicted as an embanked circular enclosure of approximately twenty metres in diameter. At some point after that survey, the bank was levelled, almost certainly by agricultural activity on the gently south-west-facing slope where it stood. The site was compiled by Denis Power and uploaded to the record in August 2011, by which time the earthwork itself had long since been reduced to its present near-invisible state.

The site sits in open pasture, so access depends on landowner permission. Because the surviving trace is so slight, a low-angled light is your best ally; early morning or late afternoon on a clear day, when shadows gather in even shallow ground, gives the depression the best chance of showing itself. There is nothing upstanding to photograph or measure in any satisfying way, and that is rather the point. What the faint outline preserves is less a monument than a record of absence, a reminder that the landscape has been read, reread, and partially erased many times over.