Bray Martello Tower, Strand Road, Bray, Co. Wicklow

The surviving tower has been converted into a private house, its thick defensive walls now topped by a glazed cylindrical structure and a glazed conical roof, so that a building designed to withstand cannon fire ends its life admitting daylight into what were once gun platforms and storerooms.

Built between 1804 and 1805, the tower belongs to a chain of coastal fortifications thrown up around the British Isles in the early nineteenth century, when invasion by Napoleonic France seemed a real and pressing danger. These squat, circular towers, named after a similar defensive structure at Mortella Point in Corsica that had impressed British engineers with its resilience, were designed with battered, sloping granite walls thick enough to deflect artillery, and only small, plain openings for defence rather than comfort. Bray's example sits on an artificial mound raised and contained by a battered stone wall, giving it something of the character of a bailey, the raised, enclosed platform found at many earlier fortified sites, though here built specifically to give the tower height and a clear line of sight over the shoreline it was meant to guard.

What makes the Bray tower worth noting today is less its original military purpose, which it shares with dozens of similar towers still standing around the Irish and British coasts, than the manner of its survival. Rather than falling into ruin or being demolished like its twin across the town, it has been adapted for domestic living, its granite bulk given a new lightness by the glass drum on top. The result is a building that reads, at a glance, as two structures in conversation: the low, defensive solidity of Napoleonic-era engineering below, and a modern, transparent addition above, both perched on the same mound overlooking the sea.