High Quality Content by WIKIPEDIA articles! Neman or Niemen or Nemunas, is a major Eastern European river rising in Belarus and flowing through Lithuania before draining into the Curonian Lagoon and then into the Baltic Sea at Klaip da. It is the border between Lithuania and Russia's Kaliningrad Oblast in its lower reaches. The 14th largest river in Europe, the largest in Lithuania and the 3rd largest in Belarus, it is navigable for most of its 900-kilometer length. The Neman River basin was formed during the Quaternary period, and is located roughly along the edge of the last glacial sheet, dating from about 25,000-22,000 BP (Before Present). Its depth varies from 1 meter in its upper courses to 5 meters in the lower basin.