The River Lagan is a major river in Northern Ireland which runs 40 miles (60 km) from the Slieve Croob mountain in County Down to Belfast where it enters Belfast Lough, an inlet of the Irish Sea. The River Lagan forms much of the border between County Antrim and County Down in the east of Ulster. It rises as a tiny fast moving stream off the Transmitter road near to the summit of Slieve Croob. From here it continues on its journey to Belfast through Dromara, Donaghcloney and Dromore.
