Built around 1790 and already designed to look derelict, Oliver's Folly is a deliberate fiction in stone, a constructed relic placed on the landscape purely for effect. The two towers are connected by a curtain wall, the whole composition built in rubble limestone with loop windows, lancet openings, and a pointed arch to the curtain wall. Everything about it mimics the appearance of a medieval fortification that has fallen into decay, except that it never existed in any other form.

Follies of this kind were fashionable among the Anglo-Irish gentry in the late eighteenth century, when a carefully composed view across one's estate, ideally including a romantic ruin on a distant hill, was considered a mark of taste and cultivation. This particular structure is associated with Castle Oliver, the residence of Richard Oliver-Gascoigne, as recorded by Fitzgerald in 1826. The folly sits 470 metres to the north-east of Castle Oliver House, which itself dates to the nineteenth century, and was annotated as "Oliver's Folly" on the Ordnance Survey's six-inch map edition of 1840, suggesting the name was already well established within a generation of its construction. It is recorded in the National Inventory of Architectural Heritage under registration number 21905615, which describes it as a freestanding, three-stage sham ruinous structure, the kind of classification that captures perfectly the paradox of something purpose-built to appear abandoned.

The folly stands within a field enclosure on the open pasture of the hilltop, and aerial photographs taken in both 1967 and 2002 show it clearly visible from above, the two towers and connecting wall still legible in the landscape after more than two centuries. Access to the site involves approaching across farmland, so it is worth being mindful of land and livestock. The elevation means the structure can be picked out from some distance on a clear day, and the surrounding pasture gives it an exposed, slightly austere quality that suits the artifice of the thing rather well.