The Great South Wall (also sometimes called the South Bull Wall), at the Port of Dublin, extends from Ringsend nearly four miles out into Dublin Bay. For many centuries, ships had problems getting into Dublin port, because there were dangerous sandbanks, its shipping channels were not deep enough and kept filling up with sand, and finally there was no shelter against high winds. It took more than 30 years to build what was to be called the Great South Wall and it was finally finished in 1795. At that time it was one of the longest sea walls in the world, remaining one of the longest in Europe. At the end of the wall stands the red-painted Poolbeg Lighthouse, standing in its current form since 1820.
While the Great South Wall protected the ships entering the harbour from wind and high waves, it could not stop the sand from filling up the shipping channels. In 1801 Captain William Bligh, the famous captain of the Bounty, suggested the construction of another wall on the northern side of Dublin Bay. The Bull Wall, as it is commonly known, was finished around 1824 and Dublin Port has never filled up with sand again.