Ireland is an island in northwest Europe in the north Atlantic Ocean whose main geographical features include low central plains surrounded by a ring of coastal mountains. The highest peak is Carrauntoohil (Irish: Corrán Tuathail), which is 1,041 metres (3,415 ft) above sea level. The western coastline is rugged, with many islands, peninsulas, headlands and bays. The island is bisected by the River Shannon, which at 360.5 km (224 mi) with a 102.1 km (63 mi) estuary is the longest river in Ireland and flows south from County Cavan in Ulster to meet the Atlantic just south of Limerick.