This 41-metre-wide platform, surrounded by a water-filled ditch and low earthen bank, appears on maps dating back to 1840, when it was depicted as a tree-covered, D-shaped mound with rounded corners. Today, the site is heavily overgrown with scrub and vegetation, making it difficult to discern its original purpose or any internal features that might once have existed.

The earthwork consists of a flat, circular area enclosed by a broad but shallow bank, with a fosse (defensive ditch) running around the outside that measures about 3 metres wide and 0.4 metres deep. The fosse widens noticeably at its southern end, though no clear entrance or causeway has been identified. When field inspectors examined the site in 1980, they found no visible internal structures or features, just the enigmatic platform itself surrounded by its watery moat.

Similar sites elsewhere in Ireland have provided tantalising clues about these mysterious earthworks. At Inchigaggin in County Cork, excavations in the 1940s revealed that what appeared to be a simple platform was actually an augmented natural feature containing three hearths and a variety of artefacts. The finds there included flints, lead fragments, glass, iron slag, and glazed pottery dating from the seventeenth century onwards, suggesting these platforms may have served as occupied sites during the early modern period. Whether the Grange Upper earthwork shares a similar history remains unknown, as it awaits proper archaeological investigation to reveal its secrets.