The Zuider Zee, also known as the Southern Sea, was a shallow bay in the northeast of the Netherlands. After the construction of the Afsluitdijk, which is a dam across the Ijsselmeer that connected the mainland to the province of Friesland, the Zuider Zee was divided into two sections - the Ijsselmeer and the Wadden Sea. The former is now a freshwater lake and the latter is a natural reserve. Synonyms for the Zuider Zee may include the Southern Sea, the South Bay, and the Zuiderzee. The region surrounding the Zuider Zee is called the Zuiderzeeland, and the towns and cities that once bordered the Zuider Zee include Enkhuizen, Kampen, and Amsterdam.