It went unrecorded on Ordnance Survey Ireland's historic mapping altogether, effectively hiding in plain sight across the farmland for generations. What it represents is a pond barrow, a form of prehistoric funerary monument defined not by a raised mound but by a deliberate hollow, where the central area is scooped inward rather than heaped up, surrounded by an encircling fosse, or ditch, that marks the boundary of the monument. This inverted logic, burial commemoration through subtraction rather than addition, makes pond barrows among the more quietly perplexing features of the Irish prehistoric landscape.

The site at Derk was identified during the Bruff aerial photographic survey in 1986, catalogued as Bruff 9, reference AP 4/3626. From the air, the form becomes legible: a circular pond barrow with an external diameter of approximately twenty-four metres, with the internal pond measuring around fourteen metres across, enclosed by an external fosse roughly two metres wide. It is one of three outlying barrows in the immediate area, the other two recorded under separate monument references, and all three sit approximately three hundred metres to the east of a ring-barrow cemetery, a cluster of circular earthen burial monuments of broadly Bronze Age date. That spatial relationship, outliers arranged near a larger ceremonial grouping, suggests the Derk barrow was part of a wider, organised funerary landscape rather than an isolated feature. Despite the 1986 identification, the monument does not appear on historic Ordnance Survey maps, and it was only confirmed through later orthoimage analysis, becoming visible in OSi imagery from between 2005 and 2012, Digital Globe imagery from 2011 to 2013, and a Google Earth image captured on 18 November 2018.

The site lies on pasture approximately ninety metres south-east of the townland boundary with Cloghaderreen, and access is across private farmland, so any visit would require landowner permission. Because the monument is so subtle at ground level, the defining features, the slight depression and the encircling ditch, are far easier to read from aerial imagery than from a field visit. Google Earth remains a useful starting point for orienting yourself before approaching the area. The broader ring-barrow cemetery three hundred metres to the west, recorded under its own monument numbers, may offer a slightly more legible sense of the prehistoric activity concentrated in this part of County Limerick, though the pond barrow itself rewards those who know precisely what they are looking for and why its apparent emptiness is the point.