The Yenisei River flows through Siberia for 2,500 miles from the Mongolian border to the Kara Sea in the Arctic Circle. This summer, the American Museum of Natural History is offering a cruise of this remote region of Russia, until recently off limits to foreigners.

An ornithologist, anthropologist, historian and several museum naturalists will accompany the trip, which is scheduled for June 26 to July 10. The itinerary includes nine nights aboard the boat, two in Moscow and two in St. Petersburg.

Rates range from $4,990 to $5,990 a person, depending on cabin type, including all meals but not air fare to Russia. Membership in the museum ($30 a year) is required for participants. For more information, call the Discovery Tours department of the museum: (800) 462-8687.