Bremerhaven is a city on the east bank of the Weser estuary in northern Germany. It forms an exclave of the city-state of Bremen. The River Geeste flows through the city before emptying into the Weser. Bremerhaven was founded in 1827 as a seaport for Bremen, and it remains one of the busiest ports in the country. It was historically rivalled by Geestemünde on the opposite side of the Geeste, which belonged to Hanover.