What the human eye struggles to read at ground level became legible only from the air, when aerial reconnaissance in July 1970 revealed the full extent of this structure, roughly 85 metres along its northeast to southwest axis and 75 metres across. It is the kind of site that exists in a strange middle ground, present and measurable but almost imperceptible.

The enclosure is defined by an inner bank, a fosse, and an outer bank, the whole arrangement forming a layered boundary that would once have been considerably more prominent. A fosse is simply a ditch, typically dug to provide material for the banks on either side of it. Here the outer bank survives most clearly along the northern side, while the rest has flattened almost to nothing. A curving bank visible in the northwest corner of the interior may indicate that the enclosed space was further divided internally. What gives the site additional interest is its relationship to the bawn of Isert Kelly Castle immediately to the south. A bawn is a defensive walled enclosure, typically associated with an Irish tower house or castle, used to protect livestock and provide a fortified outer yard. The enclosure at Castlepark extends off the northern side of that bawn, suggesting the two features formed part of a connected complex. Running further out from the enclosure, the bank along the western side continues for approximately 267 metres to the northwest, while the eastern bank extends around 135 metres to the northeast. These trailing earthworks appear to belong to an associated field system, and a possible cross bank visible on the 1970 aerial photograph hints that this outer field was subdivided as well.

From the ground today, the site asks for patience. The banks are slight, with internal heights of less than half a metre, and the fosse is only around four metres wide. The most useful way to understand the layout remains the aerial photograph taken over fifty years ago, which still shows the geometry of the whole system more clearly than any ground-level inspection is likely to.