South Island Lighthouse, Inis Oírr [Inisheer], Co. Galway

The lantern at the top sits beneath a domed metal roof with a cast-iron frame, and its drum-shaped cap carries a lightning conductor finial, a small practical detail that speaks to just how exposed this structure is to Atlantic weather. A walkway rings the lantern outside, its floor carried on painted limestone corbels and guarded by a cast-iron rail, the kind of feature that would have let a keeper check the light and glazing in conditions few people would choose to stand in.

The lighthouse was built in 1857 to a design by George Halpin Junior, whose work also stands on Rock Island west of Árainn and at Fastnet Rock, one of the most exposed light stations on the Irish coast. On Inis Oírr his hand is visible not just in the tower itself but in the ironwork throughout the complex, which is unusually accomplished for a structure built to withstand salt air and storm. Two keepers' houses were built alongside the tower, both finished to a standard that goes well beyond bare functionality, and the entire site is enclosed by a long boundary wall running the length of the access road, built of mortared coursed rubble limestone and punctuated by dressed limestone piers with plinths, caps and metal gates. A second, plainer entrance at the island's north-east end, with roughly dressed rubble piers and a wrought-iron gate, connects to a stone and mass concrete quay that served the lighthouse when it was still tended by resident keepers, allowing supplies and personnel to be landed directly below the complex.

Doorways at the base and second stage of the tower's north-west face mark the points of entry, the upper one reached by a metal stairway rather than an internal one, a design choice that kept the ground floor sealed against the sea while still allowing access higher up. The square-headed window openings, with their cut limestone sills and thick paned glass, are modest in scale but carefully finished, in keeping with the quality of stonework across the whole site. Taken together, the tower, the keepers' houses and the walled approach form a complete nineteenth-century light station, one where the ambition of the engineering is matched by the care taken over ordinary details like gateposts and window sills.