That kind of intrusion tends to happen to sites that have lost their hold on local memory, and this one in North Galway has clearly been subject to centuries of incremental erasure.

What survives is a subcircular rath, the everyday term for a ringfort, which was a type of enclosed farmstead typically built during the early medieval period, roughly between the fifth and twelfth centuries. These enclosures were defined by one or more earthen banks with a ditch, called a fosse, dug between them, and they served as the domestic and agricultural centres of rural Irish life for hundreds of years. The Aghlisk example measures approximately 46 metres east to west and 42.7 metres north to south. It originally had two concentric banks with an intervening fosse, making it a bivallate rath, a form that is sometimes associated with higher-status occupants, though the evidence here is too degraded to press that point. The inner bank is still traceable from the south around to the west and at the north-west, but elsewhere the enclosing element has reduced to little more than a scarp, a low slope in the ground rather than a proper upstanding bank. A gap at the north-west appears to be a modern break rather than an original entrance. The whole thing sits in low-lying grassland that is prone to flooding, which goes some way toward explaining both the poor preservation and why the site may have slipped from use and from notice. Waterlogged ground is hard on earthworks over the long term, and it discourages the kind of sustained activity that might otherwise have kept the memory of a place alive.