Possible Clues:

• Extensive grassland of E Europe and Central Asia
• Walk to gym in smooth flat land
• It's plain sweetheart's rejected exercise
• Grassy plain in central Europe or Asia
• Overseas plain
• Treeless plain of eastern Russia and Siberia
• Treeless grassland
• Grassland area
• America’s prairies are examples of this type of landscape
• Plain foot movement needed with gym