at altitude and the Biała ("White") Wisełka at altitude . Both are on the western slope of Barania Góra in the Silesian Beskids in Poland. Geography The Vistula can be divided into three parts: upper, from its sources to Sandomierz; central, from Sandomierz to the confluences with the Narew and Bug; and bottom, from the confluence with the Narew to the sea. The Vistula river basin covers (in Poland ); its average altitude is above sea level. In addition, the majority of its river basin (55%) is 100 to 200 m above sea level; over of the river basin ranges from in altitude. The highest point of the river basin is at (Gerlach Peak in the Tatra mountains). One of the features of the river basin of the Vistula is its asymmetry—in great measure resulting from the tilting direction of the Central European Lowland toward the northwest, the direction of the flow of glacial waters, and considerable predisposition of its older base. The asymmetry of the river basin (right-hand to left-hand side) is 73–27%. The most recent glaciation of the Pleistocene epoch, which ended around 10,000 BC, is called the Vistulian glaciation or Weichselian glaciation in regard to north-central Europe. Major cities Delta The river forms a wide delta called Żuławy Wiślane, or the "Vistula Fens" in English. The delta currently starts around Biała Góra near Sztum, about from the mouth, where the river Nogat splits off. The Nogat also starts separately as a river named (on this map ) Alte Nogat (Old Nogat) south of Kwidzyn, but further north it picks up water from a crosslink with the Vistula, and becomes a distributary of the Vistula, flowing away northeast into the Vistula Lagoon (Polish: Zalew Wiślany) with a small delta. The Nogat formed part of the border between East Prussia and interwar Poland. The other channel of the Vistula below this point is sometimes called the Leniwka. Various causes (rain, snow melt, ice jams) have caused many severe floods of the Vistula down the centuries. Land in the area was sometimes depopulated by severe flooding, and later had to be resettled. See (Figure 7, on page 812 at History of floods on the River Vistula) for a reconstruction map of the delta area as it was around the year 1300: note much more water in the area, and the west end of the Vistula Lagoon (Frisches Haff) was bigger