Someone at some point quarried the interior away, leaving a rectangular flat-bottomed pit where the heart of the site once was, and piled the spoil along the top of the surrounding bank. The result is an earthwork that simultaneously preserves and confuses its own outline.

The enclosure at Masreagh measures roughly 19 metres north to south and 18 metres east to west, defined by a scarp, a steep earthen edge rather than a built wall, that rises to 0.8 metres on the east side and to a considerably more substantial 2.3 metres on the west. That asymmetry likely reflects the natural slope of the ground as much as any deliberate construction. There is no fosse, the external ditch that typically accompanies this kind of enclosed platform, visible at ground level, and no trace of an original entrance survives. The quarrying that hollowed out the interior left a depression measuring approximately 12 metres by 10 metres and dropping around 0.4 metres below the surrounding floor level. Whether this was stone extraction, gravel digging, or something else entirely is not recorded, but the activity was substantial enough to remove whatever archaeology once lay beneath the surface and to reshape the silhouette of the monument in the process. Circular enclosures of this type are found widely across Ireland, often interpreted as ringforts, which were enclosed farmsteads used primarily from the early medieval period, though their dates and functions vary considerably from site to site.