The Great South Wall, also called the South Bull Wall, at the Port of Dublin, extends from Ringsend over 4 Km out into Dublin Bay.
It was the world's longest sea wall at the time of its construction and remains one of the longest in Europe.
It faces the newer Bull Wall, and has one of a trio of port lighthouses at its end.
Dublin Bay had a long-running problem with silting, notably at the mouth of the River Liffey.
It held major sand banks, notably the North Bull and South Bull, both hard sand dry at low water, to either side of the Liffey mouth, along with the Kish Bank over 11 km out to sea.
Between the North and South Bulls, a sand bar existed, rising over time, limiting access to the city quays.