In times past, there were many unmarked rocks in the river between Monkstown and Passage West. Many a ship foundered on these rocks. The best known and the most hazardous was the Giant’s Stairs at Monkstown. These were seven huge shelves of rock rising from the sea to a cave, known as the Giant’s Cave.
Legend tells us that a great giant named Mahon MacMahon used these steps and lived in the cave. He captured young boys and trained them to work with various metals. Thomas Crofton Croker wrote a story, “The Giant’s Stairs”, in Fairy Legends of Ireland. The main character, Philip Ronayne, was the well-known mathematician who lived at Ronayne’s Grove on the Great Island who, in 1717, published a famous work on algebra. He died at his home on the 23rd April 1775. Ronayne’s Court in Rochestown was the oldest house on the River Lee. Now all that remains of it is the fine old limestone fireplace which was moved to Blackrock Castle.
The Giant’s Stairs was cut through in the 1830s when the railway line and the R610, now the main road between Monkstown and Glenbrook, were being built. This cave became a refuge for smugglers and was closed in 1835.