The only way to detect it is from the air, specifically through Google Earth imagery captured in July 2018, where it appears as a cropmark, a ghostly outline in the vegetation caused by the differential growth of plants over buried archaeological features beneath the soil.

What the imagery reveals is a roughly circular enclosure about ten metres in diameter, defined by a continuous shallow fosse, the term for a ditch or trench of the kind commonly used to demarcate enclosed spaces in early Irish archaeology. The site sits at the base of a south-east-facing slope, and roughly forty metres to the south-east another cropmark records what appears to be an old meander or curve of the Slaney, a former channel the river has long since abandoned. A related ring-ditch, a circular ditched feature often associated with prehistoric burial or ritual activity, lies approximately seventy-five metres to the south. The enclosure at Kilcannon was first identified by Simon Dowling, whose observation brought this otherwise invisible feature to wider attention.