The ring-barrow at Knockderk, a circular earthen mound of the kind raised over burials during the Bronze Age, does not appear on any of the Ordnance Survey Ireland historic mapping series. It existed in plain sight in the fields, quietly overlooked, until a camera mounted in a survey aircraft finally gave it away.

The site came to light during the Bruff aerial photographic survey of 1986, catalogued under reference Bruff 95 (AP 4/3616), when the characteristic circular outline of a ring-barrow became legible from the air. A ring-barrow typically consists of a low central mound enclosed by a surrounding ditch, a form of funerary monument associated broadly with prehistoric burial practice. At Knockderk, the monument sits in wet pasture approximately 220 metres east of the townland boundary with Ballynagreanagh. Its presence was confirmed again in more recent decades, appearing as a circular cropmark, roughly 8.5 metres in diameter, on Ordnance Survey Ireland orthophotos taken between 2005 and 2012, and on a Google Earth image dated 18 November 2018. A cropmark of this kind forms when buried features affect how plants grow above them, causing a faint but readable difference in vegetation colour or density that becomes visible from above, particularly in dry spells. The record was compiled by Martin Fitzpatrick and uploaded in April 2021.

Because the monument is set in wet pasture and has no surface expression that would be legible to a casual visitor on foot, there is little to see at ground level. The location is best appreciated through the aerial and satellite images associated with the survey record, where the circular outline reads clearly against the surrounding field. Anyone wishing to visit the general area should be aware that the land is private agricultural ground, and the site itself offers no upstanding earthwork to observe. The cropmark is most likely to be visible in aerial or satellite imagery captured during dry summer conditions, when soil moisture differences above buried features are at their most pronounced.