The Spreewald (German for "Spree Woods"; in Lower Sorbian: Błota) is situated about 100 km south-east of Berlin. It was designated a biosphere reserve by UNESCO in 1991. It is known for its traditional irrigation system which consists of more than 200 small canals (called "Fließe"; total length: 1,300 km ) within the 484-square-kilometre (187 sq mi) area. The landscape was shaped during the ice-age. Alder forests on wetlands and pine forests on sandy dry areas are characteristic for the region. Grasslands and fields can be found as well.