The site at Porterstown is not marked by any standing stone or interpretive panel; its existence is known almost entirely from what could not be seen at ground level, only from the air and from instruments pushed into the earth.

Aerial photography first revealed the site as a cropmark, the kind of faint discolouration in growing crops or grass that betrays buried features to a camera pointed downward from a light aircraft. The photograph, catalogued as CUCAP AVS 30, showed a roughly circular enclosure approximately 40 metres in diameter, consistent with a ringfort, the ubiquitous enclosed farmsteads of early medieval Ireland, typically defined by one or more earthen banks and ditches. Ahead of car park construction at Porterstown church, a partial excavation was carried out in 1990, directed by Cotter and reported in 1991. Archaeologists located the fosse, the encircling ditch, finding it round-bottomed, between 2.5 and 3 metres wide and 1.25 metres deep. Its fill was largely sterile, yielding little beyond some animal bone, though a possible entrance gap on the eastern side was identified. The earthworks themselves had been levelled long before anyone thought to look. Older still, a gully and a scatter of post-holes containing a sherd of Bronze Age pottery suggested that people had made use of this ground well before any ringfort was constructed here.

A geophysical survey carried out in 2006 under licence 06R180, by Krahn, extended the picture further, establishing that the eastern portion of the ringfort actually continues beneath the playing pitches adjoining the car park. A sports club was later built to the south, accessed by a pathway that cuts across the site, and it remains unclear whether the laying of services associated with these developments disturbed any surviving subsurface deposits. For anyone visiting, there is nothing visible above ground. The interest lies precisely in that absence, in standing at an ordinary car park or watching a game of football on a pitch and knowing that the curved line of a ditch from perhaps a thousand or more years ago runs quietly underneath.