The Tumen is a 521-kilometre river in Northeastern Asia. The Tumen flows between Russia, North Korea and China and serves as part of the boundary between these three countries. In this stretch, you can start at North Korea, and few miles later, you will pass through China and end up in Russia before entering the Sea of Japan. It’s a common place for North Koreans to attempt to defect and, for that reason, it is heavily patrolled by North Korean soldiers. The name of the river comes from the Mongolian word ‘tümen’ meaning ten thousand. The Russian name of the river is Tumannaya, which means ‘foggy’.