The geography of Ireland describes an island in northwest Europe in the North Atlantic Ocean. The main geographical features of Ireland include low central plains surrounded by a ring of coastal mountains. The highest peak is Carrauntoohil (Irish: Corrán Tuathail), which is 1,041 m (3,414 ft) above sea level. The western coastline is rugged, with many islands, peninsulas, and headlands. The island is bisected by the River Shannon, which at 259 km (161 s) with a 113 km (70 miles) estuary is the longest river in Ireland and flows south from County Cavan in the north to meet the Atlantic just south of Limerick.