Zulawy Wislane (fens, plural from "zulawa") is the alluvial delta area of Vistula, in large part reclaimed artificially by means of dykes, pumps, channels (over 17000 km of total length) and extensive drainage system. In shape similar to reversed triangle formed by branching of Vistula into two separate rivers, Leniwka and Nogat at its height, confined by rivers themselves, and closed by Mierzeja Wislana at its base. It is a deforested, agricultural plain that covers 1000 square km.