What exists here is visible only from the air, and only under the right conditions: a circular enclosure roughly thirty metres across, betrayed not by any upstanding stonework or earthen bank but by the faint differential growth of crops above a buried ditch.

This kind of feature is known as a cropmark, and it forms when a fosse, the term for an ancient ditch or trench, is cut into the subsoil and later fills with looser, more moisture-retentive material. Crops growing over that buried fill tend to grow taller and greener than those in the surrounding ground, tracing the original shape of the ditch in miniature above it. In dry summers especially, the contrast becomes legible from altitude. The enclosure at Wallslough was picked up on aerial photographs taken in July 1996 and again in July 2000, both surveys catching the cropmark during the kind of dry period that makes such features most apparent. The circular form and the presence of a fosse are consistent with a ringfort, a type of enclosed farmstead common across Ireland from the early medieval period, though the site has not been excavated and no more precise dating is available from what has been recorded.