(Dutch; " Southern Sea ")
Former inlet of the North Sea , northern coast of The Netherlands.
From the 13th to the 20th century, it penetrated The Netherlands and occupied 2,000 sq mi (5,000 sq km), separated from the North Sea by an arc of former sand flats that are now the West Frisian Islands. Frisian peoples inhabited the sand flats from 0441; AD 400 and built the first sea works, considered engineering marvels, to stem rising sea levels. The control of water levels within the dikes developed into the reclamation of lowlands (polders) from the water. Between 1927 and 1932 a dam 19 mi (30 km) long was built across the Zuiderzee, separating it into the Waddenzee and the IJsselmeer. By the early 1980s four polders (of five proposed), largely agricultural land, had been created.