This 43 000ha polder, mostly drained in 1968, is separated from Oostelijk Flevoland by a safety dike, the Knardijk. It is surrounded by a dike built from 1959 to 1967. Half the land is given over to agriculture, the rest to living space, breeding animals, woods, dikes and roads. The Oostvaardersplassen nature reserve was created close to the Oostvaardersdijk to the north of the polder. This marshy land is a refuge for many birds.