Possible Clues:

• Crossing the Tiber, I abandon peninsula
• Disease reduced by exactly 50% in one area, part of Europe
• Peninsula that was Roman province
• Timeless classical river by capital flowing west in peninsula
• Mediterranean peninsula
• Part of Europe like very cold part of Asia, avoiding the extremes
• Pamplona's peninsula
• Albéniz piano work
• Airline to Madrid
• Spain and Portugal, together