The Great South Wall, at the Port of Dublin, extends from the tip of the Poolbeg peninsula more than four kilometres 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 four port lighthouses at its end.

Dublin Port is the seaport of Dublin, Ireland, of both historical and contemporary economic importance. Approximately two-thirds of Ireland's port traffic travels via the port, which is by far the busiest on the island of Ireland.