Ballydonnellan Castle, Ballydonnellan East, Co. Galway

Step through the round-headed doorway, though, and the geometry changes entirely: the interior is circular, its brick-lined walls fitted with tier upon tier of nesting boxes. The mismatch between the square exterior and the drum-shaped interior was a deliberate piece of design, since a circular plan makes the most efficient use of wall space for roosts, and this is, in essence, a dovecote built to house working birds rather than ornament a landscape.

Dovecotes like this one were a common feature of Irish demesnes into the eighteenth century, when pigeons were kept not for sentiment but for sustenance: their flesh and eggs supplemented the table, and their droppings, rich in nitrogen, were valued as manure at a time before chemical fertilisers. This example, dating from around 1750, once stood roofed and functioning within the wider demesne of Ballydonnellan Castle, part of a scattered group of estate structures that also included a house, a walled garden, outbuildings and entrance gates. It is now roofless and ruinous, but enough survives to read its construction clearly: a tooled limestone surround with two arch stones frames the doorway, and above it a square recess breaks the wall face, a small decorative touch on an otherwise workmanlike building. That doorway is thought to have been reused from the nearby towerhouse, the fortified stone residence typical of late medieval Ireland, which would make this modest dovecote a repository of older masonry as well as a functional farm building in its own right.

Seen today, the dovecote is easy to overlook against the more obvious ruins of the castle and house nearby, yet it rewards a closer look precisely because its plainness conceals that inner circle of brick nesting boxes, a quietly ingenious solution to a very practical problem, tucked inside four unassuming stone walls.