Top Things to do in Spain: The vibrant flea market at El Rastro in Madrid, Valencia's bustling Barrio del Carmen nightlife, Pamplona Bull Running's intrinsic fear, Buol's La Tomatina festival's pure joy, La Feria de Sevilla's flamenco festival's weeklong joy, or the enjoyment of tapas or wine, the constant fiestas or siestas, and of course, the…