SELENGA-ORKHON, a river of Central Asia, which rises in two principal head-streams, the Selenga and the Orkhon, on the plateau of N.W. Mongolia, not far apart in 101 E. Both flow generally E.N.E. as far as their confluence near Kiakhta, on the frontier of Mongolia and Siberia, at the eastern extremity of the Sayan Mountains. Beyond Kiakhta the river flows generally N. nearly as far as 52 N., when it turns W. and enters Lake Baikal on the S.W., forming a delta. It is navigable from Kiakhta downwards, a distance of 210 m., its total length being 750 m. From the left it receives the Eghin-gol and the Jida, and from the right the Tala, Kharagoy, Chikoy, Khilok and Uda, streams each 150 to 300 m. in length. Near the upper Orkhon was the permanent camp of Karakorum, from the 8th century down to the end of the 13th the centre of the Mongol power, especially under the sway of Jenghiz Khan and his son Ogotai or Ogdai in the 12th and 13th centuries.
Several remarkable inscriptions were discovered here in the end of the 19th century, and were interpreted by Professor V. Thomsen of Copenhagen Inscriptions de I'Orhhon (Helsingfors, 1900).
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)