Marked on Ordnance Survey maps from 1834 and 1907 in gothic lettering as a castle in ruins, and described by the surveyor Charles Coote in 1801 as an old building with "a curious whimsical appearance" that "seems to be very ancient", it has also attracted a local tradition linking it to the McMahon clan, the Gaelic lords who once dominated County Monaghan. None of this is accurate. What stands in the trees is a folly, a deliberate architectural fake, built on the demesne of Castleblayney to look like a romantic ruin.

A folly, in the eighteenth and nineteenth-century landscape tradition, was a decorative structure built purely for visual effect, often designed to evoke antiquity, melancholy, or the picturesque from across a lawn or lake. This one is modest in scale but carefully composed. The building is roughly six metres square in plan, with a circular tower centrally placed in each of its four walls. The north-western tower survives to a height of around three metres and retains two narrow openings, each fitted with pointed brick arches, which give the structure its vaguely medieval character. The other three towers have fared less well, surviving to only about a metre in height, though lintel openings remain visible in the north-eastern and south-eastern towers. An internal dividing wall is still present, and the original entrance and staircase are thought to have been on the north side. The south-western tower has been largely destroyed. The use of brick arches within a stone shell is a detail worth noting: it points clearly to deliberate construction rather than genuine antiquity, and sits oddly against the mossy woodland setting that has since grown up around it.