Overgrown and shapeless, it sits in a field and gives little away at first glance. Mixed into its mass, however, are burnt stone and charcoal, the characteristic signature of what archaeologists call a burnt mound, a type of site found across Ireland and Britain that is generally associated with prehistoric activity, most likely involving the repeated heating of stones and their disposal after use, possibly for cooking, bathing, or industrial processes. The stones crack and shatter when heated and then cooled, which is why they accumulate in such quantities and why the mounds they form are so recognisable to those who know what to look for.

The mound at Lissooleen appears to have become entangled with more recent agricultural history. When the site was examined in the mid-1990s as part of a survey of the Lee Valley area, it was interpreted as the result of field reclamation on that side of the ground, with the burnt stone and charcoal incorporated into a general clearance mound. In other words, at some point a farmer clearing the field may have gathered older archaeological material along with everything else, folding prehistoric debris into a much more mundane act of land improvement. Whether the original burnt mound deposit was already present on the surface or was turned up during cultivation is not recorded, but the mixture of ancient and agricultural is a common enough story in the Irish landscape, where millennia of human activity tend to layer on top of one another with little ceremony.