When the Ordnance Survey mapped the area in 1839, their six-inch map recorded a triple-banked enclosure with an external diameter of around sixty metres. By the time the surveyors returned for the 1925 edition, that same feature had been redrawn as something quite different: a D-shaped enclosure. Whether the landscape changed between those two surveys, or whether the earlier cartographers were simply more ambitious in their reading of the ground, is no longer easy to say.

What survives today is a raised D-shaped area measuring roughly forty metres across on its north-east to south-west axis, now planted with coniferous trees. An embanked enclosure of this kind is essentially a defined area of ground ringed by a built-up earthen bank, sometimes accompanied by a ditch or fosse on the outside, and in Ireland such features can range in date and purpose from early medieval farmsteads to prehistoric ceremonial sites. At Brownstown, the bank itself is only partially legible: slight traces run along the south-east to west arc, while elsewhere the enclosure is marked by a natural-looking scarp, a low edge or slope in the ground, ranging from about 0.6 to 1.6 metres in height. There is no visible fosse, and no identifiable entrance has been found. A field bank running north-west to south-east has cut across the north-eastern portion of the enclosure, further obscuring whatever form it once held.

The combination of tree cover, truncation by a later field boundary, and the gradual softening of earthworks over centuries makes Brownstown an example of how much archaeological detail can be lost not through dramatic event but through ordinary agricultural use and the slow work of time.