The Vltava is the longest river in the Czech Republic – 430 kilometres long from its source in Šumava to confluence with the Elbe (Labe in Czech) at Mělník. It flows northward for most of its course. It drains about 28,090 km2; at the confluence it actually has more water than the Elbe, but Vltava joins the Elbe at a right angle to its flow so that it appears a mere tributary and for historical reasons the river after the confluence is called Elbe. Biggest tributaties of Vltava are Berounka (which joins Vltava in the southern part of Prague), Sázava, Otava and Lužnice. Apart from Berounka, there are several streams in Prague which flow into Vltava, the biggest of them being Rokytka and Botič, others incude Brusnice, Šárecký potok and Dalejský potok.
In Prague, the course of Vltava is 31 kilometres long and the river is crossed by 18 bridges (11 road bridges, 5 railway bridges (including one tramway bridge) and 2 pedestrian bridges (including the famous medieval Charles Bridge)). There are several weirs and locks on Vltava, so the river is navigable in Prague.
In August 2002 there was a great flood of Vltava, which killed several people and caused massive damage and disruption along its length. The Prague metro system was partially flooded and it took several months to open the damaged stations.