The Shannon Estuary (Irish: Inbhear na Sionainne) is a large estuary where the River Shannon flows into the Atlantic Ocean. The estuary has Limerick City at its head and its seaward limits are marked by Loop Head to the north and Kerry Head to the south. The estuary defines the main boundary between County Kerry/County Limerick to the south and County Clare to the north. In the second half of the 19th century about 65 km² of the estuary's lowlands have been embanked and reclaimed, largely for agricultural purposes.