There is no earthwork to speak of, no mound, no upstanding wall. The only way to perceive its shape is from above, where the crop stress of a buried ditch draws a ghostly arc across a tillage field, a phenomenon known as a cropmark. In dry conditions, soil above a filled ditch retains moisture differently from the surrounding ground, causing the vegetation above it to grow taller or stay greener, producing a contrast that is legible from satellite imagery even when nothing at ground level gives the site away. What emerges at Tankardstown is a subcircular enclosure roughly 68.5 metres north to south and 59.5 metres east to west, its perimeter ditch somewhere between two and two and a half metres wide, curving from the north-west around through the east and back down to the south-west.

The western arc of the enclosure does not show clearly on available imagery, which may simply reflect the state of the field at the time of capture, with hay recently cut along the margins. Whether an entrance gap exists to the west, close to the Guilie River, remains uncertain. The Guilie meanders around the site and makes a noticeable change of direction roughly 150 metres to the south, suggesting the enclosure may have been deliberately positioned in relation to the river's course. The broader landscape here slopes gently southward towards the River Barrow, about 2.1 kilometres to the east at its nearest point. The site sits at around 65 metres above sea level in gently undulating terrain that is now given over to mixed pastoral and tillage farming. It does not exist in isolation: approximately 675 metres to the south lie the remains of an early church site at Kilabban, associated with St Abban, an early Irish saint, and around 550 metres to the west-north-west another cropmark enclosure, a bivallate type with two concentric ditches, has been identified at Coolgarragh. The clustering of these features points to a stretch of the Laois lowlands that was once considerably more organised and inhabited than its present agricultural appearance suggests.