Curonian Lagoon

The Curonian Lagoon forms a broad freshwater expanse behind the Curonian Spit, measuring about 1,619 square kilometres while averaging only 3.8 metres in depth. The Neman River supplies roughly 90 percent of its inflow, drawing water from a watershed spread across Lithuania and the Kaliningrad region. At the northern end, the Klaipėda Strait provides the narrow passage into the Baltic. The spit screens the lagoon from open-sea waves, so its shallow water, muddy bottom, and sheltered margins create conditions unlike those on the coast beyond.

In the thirteenth century, the surrounding lands belonged to Baltic Curonians and Old Prussians and bordered the later region of Lithuania Minor. The strait gave strategic importance to the northern outlet. In 1252 the Teutonic Knights founded Memelburg Castle and the settlement that became Klaipėda there, using the passage as a gateway between inland waterways and the sea. The castle and port made the lagoon’s northern mouth a point where political control, shipping, and regional trade met.

The lagoon was formed in its present broad form about 7,000 BCE and supports high biodiversity despite its shallow basin. Pollution and algal blooms in later times reveal how readily a nearly enclosed body of freshwater absorbs pressures from its tributaries. Reeds, fishing grounds, and seasonal migration routes combine around shores divided by later national borders. The water therefore belongs to an older Baltic world of movement, but also to the intimate ecology of a shallow inland sea.