The Váh is a left tributary of the Danube River in Slovakia. It is the longest (403 km) and main river of Slovakia. Its two sources, the Biely Váh (White Váh) and the Čierny Váh (Black Váh), are located in the High Tatrass and in the Lower Tatras (Nízke Tatry) , respectively, and it flows over northern and western Slovakia and finally pours into the Danube near Komárno. It includes canals, artificial lakes and 16 hydropower stations, whose construction started in the 1930’s and especially after World War II. Major Slovak towns are situated at this river, e. g. Ružomberok, Martin, Žilina, Považská Bystrica, Púchov, Dubnica nad Váhom, Nové Mesto nad Váhom, Piešťany, and Komárno. Also, the main Slovak limited-access highway is situated along the Váh.