A ringfort once occupied this summit, a type of enclosed farmstead typically dating from the early medieval period, built by a single family or small community and marked by a circular earthen bank or stone wall. At Addinstown, the earthworks have been completely levelled, leaving the hilltop open to the sky and the surrounding countryside visible in every direction.

The site's earlier form is recoverable only through old maps. The 1837 Ordnance Survey Fair Plan recorded a circular enclosure on the hill, with a rectangular ruin inside it, the cartographers annotating both features plainly as 'fort' and 'ruins'. By the time the 1838 six-inch Ordnance Survey edition was prepared, the enclosure was shown sitting inside a square tree plantation, one established after 1700, suggesting the land had been reorganised in the post-medieval period, the fort incorporated into a designed landscape associated with Addinstown House, which stands around 190 metres to the northwest. A trigonometric point was later placed in the southwest quadrant of the monument, one of the brass or concrete survey markers used to establish precise elevations across the country, and it remains the most visible object on the site today.