Markermeer

The Markermeer is a 700 km2 lake in the central Netherlands in between North Holland, Flevoland, and its smaller and larger neighbors, the IJmeer and IJsselmeer. A shallow lake at 3 to 5 m in depth, matching the reclaimed land to its west, north-west and east it is named after the small former island, now peninsula, of Marken on its west shore.

The Markermeer was not originally intended to remain a lake. It was formerly part of the Zuiderzee, a saltwater inlet of the North Sea, that was dammed off by the Afsluitdijk in 1932, turning the Zuiderzee into the freshwater IJsselmeer. The following years saw the reclamation of extensive tracts of land as large polders in an enormous project known as the Zuiderzee Works.

Source: Wikipedia