Dublin, the capital of the Republic of Ireland, is located on the east coast of Ireland at the mouth of the River Liffey. Its historic buildings include Dublin Castle, dating from the 13th century, and the imposing St. Patrick's Cathedral, built in 1191. The city's attractively landscaped parks include St Stephen's Green and the sprawling Phoenix Park, home to the Dublin Zoo. The National Museum of Ireland explores the culture and heritage of Ireland.