Croagh Patrick is an isolated mountain that rises about 2,500 feet (760 meters) above sea level in County Mayo, in the Republic of Ireland. In Irish, the mountain is called Cruach Phádraig. It is also known as “The Reek.” Irish Roman Catholics regard Croagh Patrick as a holy mountain because Saint Patrick is said to have spent 40 days in prayer and fasting on its summit, praying for the success of his mission in Ireland. Patrick, who became the primary patron saint of Ireland, was chiefly responsible for converting the Irish people to Christianity. On the last Sunday of July—Reek Sunday—thousands of pilgrims climb the mountain to attend Mass in the tiny oratory (room used for prayer). See also Mayo, County; Patrick, Saint.