County Mayo is a sparsely populated county on the west coast of Ireland. Known for its natural beauty and for being the home of a mountain on which St. Patrick is said to have fasted, it is also known for being the site of some of the heaviest waves of Irish emigration. Though the county is sparsely populated today, Irish settlers in many other parts of the world still trace their roots back to County Mayo. County Mayo's largest city has just over 10,000 residents, the city of Castlebar. Ashford Castle, built in the 1200's, is a testament to medieval architecture. Not all castles are associated with royalty and Rockfleet Castle near New port was a home to Grace O'Malley, a famous pirate queen.