The Gudbrand Valley (Norwegian: Gudbrandsdalen) is a valley and traditional district in the Norwegian county of Oppland. The valley is oriented in a north-westerly direction from Lillehammer and the lake of Mjøsa, extending 230 kilometers (140 mi) toward Romsdalen. The river of Gudbrandsdalslågen (Lågen) flows through the valley, starting from Lesjaskogsvatnet and ending at Mjøsa. The Otta river flowing through Otta valley is a major tributary to Lågen. Together with Glomma river and Østerdalen, Lågen and the Gudbrand Valley forms Norway's largest river/valley system. The Gudbrand Valley is home to Dovre Line and the E6 road, and is the main land transport corridor through South Norway, from Oslo and central eastern lowlands to Trondheim and Møre og Romsdal.