The Polish Baltic coast is mostly smooth but has natural harbors in the Gdańsk-Gdynia region and Szczecin in the far northwest. This coast has several spits, dunes and coastal lakes. Coast lakes are former bays that have been cut off from the sea. These areas are sometimes called lagoons. Szczecin Lagoon is on the western border with Germany. The Vistula Lagoon is on the eastern border with Kaliningrad, province of Russia. The longest river in Poland, the Vistula river, empties into the Vistula Lagoon and also directly into the Baltic Sea.