Possible Clues:

• Russian river flowing into the Caspian Sea
• Longest European river, flowing into the Caspian Sea
• The world’s longest river flowing into an inland body of water rather than the sea
• Europe’s longest river
• Russian river that discharges into the Caspian Sea
• Russian river (longest in Europe)
• Gorky Reservoir river
• Russian river, the longest in Europe
• River through western Russia
• Very popular Slavic name for Russian river