Lough Derg is the name of two famous lakes in the Republic of Ireland. Lough Derg in County Donegal is famous for the Lough Derg Pilgrimage. Saint Patrick is supposed to have spent 40 days in prayer and fasting on a small island in the lake. Thousands of people visit the island each year to fast and pray.
The other Lough Derg is the largest lake on the River Shannon. It measures about 25 miles (40 kilometers) in length and from 2 to 3 miles (3.2 to 4.8 kilometers) in width. The lake lies between the provinces of Connacht and Munster.
