Poolbeg Lighthouse, Dublin

Poolbeg Lighthouse is the vivid maritime landmark at the mouth of the River Liffey, where it still serves as an active aid to navigation. Its story reaches back to 1767, when the light began with candles; in 1786, oil replaced that arrangement. The structure you see was redesigned and rebuilt in 1820, giving the beacon its present shape.

It stands at the end of the Great South Wall, a long stone barrier extending into Dublin Bay from the Poolbeg peninsula. The lighthouse is painted red, matching the channel-marking system used for vessels travelling upstream. For many years it has operated automatically, under the care of Dublin Port Company. There is also a quiet surveying connection: the spring-tide low-water mark recorded here on 8 April 1837 served as the height reference for Ordnance Survey Ireland maps until 1958.