When you think of windmills, the Netherlands might first come to mind. But some of the oldest windmills in the world are in Nashtifan, Iran. Dozens stand atop a wall in the windy city, not far from the Afghanistan border. From a distance, they look like wooden turnstiles. But they are vertical-axis windmills constructed over 1,000 years ago from wood, straw and clay. For centuries, they were used to mill flour. In 2002, the windmills of Nashtifan were declared a national heritage site by Iran.