The Lena is a river in the Russian Far East and is the easternmost river of the three, great rivers of Siberia, including the River Ob and the River Yenisey, which flow into the Arctic Ocean. The Lena river is 4,294 km long and has a capacious drainage basin of 2,490,000 km² ; thus the Lena is the eleventh-longest river in the world and the longest river entirely wi…The Lena is a river in the Russian Far East and is the easternmost river of the three, great rivers of Siberia, including the River Ob and the River Yenisey, which flow into the Arctic Ocean. The Lena river is 4,294 km long and has a capacious drainage basin of 2,490,000 km² ; thus the Lena is the eleventh-longest river in the world and the longest river entirely within Russia. Geographically, permafrost is the type of soil that underlies most of the Lena river's catchment, twenty per cent of which is continuous.