Individual #Ob_River__Ob  a Russian river; flows northward to the Arctic Ocean
  instance of:  #river
  part of:  #Siberia  a vast Asian region of Russia; famous for long cold winters
     part of:  #Russia__Russian_Federation  a federation in northeastern Europe and northern Asia; formerly Soviet Russia; since 1991 an independent state
        part of:  #Eurasia  the land mass formed by the continents of Europe and Asia
           part of:  #eastern_hemisphere__easternhemisphere__orient  the hemisphere that includes Eurasia and Africa and Australia
           part of:  #northern_hemisphere  the hemisphere north of the equator

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