Possible Clues:

• 1500-mile river to the Caspian Sea
• Europe/Asia boundary river
• ___ Mountains (they divide Europe and Asia)
• The Ilek is one of its tributaries
• Mountains in Russia
• Nat would not have been affected by such an range
• River through the Steppes of Asia
• Russia river
• River separating continents
• __ Mountains (Eurasian range)