A bawn was the defended courtyard attached to a castle or fortified house, typically walled in stone and reinforced at the corners to allow defenders to cover every angle of approach. At Carlanstown, that defensive logic is still partially legible in the landscape: three circular corner towers remain upstanding at the south-west, north-west, and north-east angles of the square enclosure, while the fourth, at the south-east, is gone, as is the gateway that once pierced the east wall.

The castle or fortified house that originally occupied the southern half of the bawn has left no visible trace above ground, replaced long ago by post-1700 farm buildings and a farmyard that now fill the interior. Carlanstown House, a multi-period structure, runs along the line of the demolished south wall. What does survive from the earlier period is stranger and more easily overlooked: a square-headed doorway set into the south wall of the stables carries a date stone of 1813, but the two scroll brackets framing it are thought to belong to a much earlier moment, possibly the late seventeenth or early eighteenth century. The working assumption is that these brackets were salvaged from Carlanstown Castle itself and incorporated into the later stable building, giving an otherwise unremarkable agricultural doorway an oddly layered history. It is the kind of reuse that was entirely practical at the time and is now, inadvertently, the most eloquent piece of evidence remaining for a structure that otherwise left nothing standing.