The Lena is the main waterway of eastern Siberia and is the longest river in Russia. The river originates in the Baikal Mountains and flows northeast for 2,700 mi (4,300 km) where it empties into the Arctic Ocean through the Laptev Sea. The river is complexly braided and drains an area of about 1 million mi2 (2.6 million km2). Chief tributaries are the Vitim, Olekma, Aldan, and Vilyuy Rivers. The delta is approximately 250 mi (402 km) wide. As the second largest river in Russia in terms of water discharge, the Lena transports large amounts of dissolved and particulate material into the Arctic seas.