The source of the Dubysa river is located near Šiauliai. The river crosses the Žemaitija Upland, flowing into the Nemunas near Seredžius village. The water level in Dubysa varies greatly and is influenced by both melting snow and rainwater collected by the rivers and streams of the Žemaitija Upland. It is not for nothing that this river is very popular with water tourists. In summer it has a calm flow, the river is clear, the bottom is sandy in most places, which makes Dubysa very suitable for peaceful swimming. The Dubysa river valley is one of the deepest (20–40 m) and widest (up to 0.5 km) in Lithuania, formed by a glacier. During the Russian Empire in 1825, a project was launched to connect Dubysa with Venta via the so-called Venta–Dubysa Canal or Vindava Canal. The work was carried out by 18,000 soldiers and 3,000 civilians. The purpose of the canal was to connect the Nemunas basin with the Baltic Sea and the port of Ventspils, because the lower reaches of the Nemunas were under Prussian control at that time. These works were disrupted by various historical events, including the First World War, after which the canal lost its significance as Lithuania acquired land in the lower reaches of the Nemunas. Back in the 1970s, the canal was used for rowing competitions, but today it is abandoned and overgrown, although it is declared a cultural monument.