No earthwork rises from the grass, no ditch catches the evening light, no obvious feature interrupts the improved pasture on its east-facing slope. The only evidence that something is there at all came from the air, when an aerial photograph taken in May 2003 revealed a circular cropmark, the kind of faint discolouration in growing vegetation that betrays buried archaeology beneath. Crops and grasses respond differently to soil that has been disturbed in the past, even thousands of years ago, and under the right conditions of drought or rapid growth, the outline of a long-vanished structure can briefly reappear, visible only from altitude.

The photograph showed not just a single circle but a more complex arrangement: the circular enclosure appears to have a second, conjoined enclosure attached to its western side. Enclosures of this kind are often associated with early medieval settlement in Ireland, used to define and protect a homestead or agricultural space. The site does not stand alone in the landscape either. Roughly 110 metres to the north-west lies a ringfort, a type of enclosed farmstead typically dating from the early medieval period, roughly the fifth to the twelfth centuries. The proximity of the two features suggests this part of Mortlestown may once have been a more densely organised and inhabited place than the quiet pasture there today would suggest.