This photo taken on May 9, 2026 shows the De Valk windmill in Leiden, the Netherlands. Dutch National Mill Day is celebrated annually on the second weekend of May, when windmills and watermills across the Netherlands open to the public. Visitors can enjoy guided tours, live demonstrations, and spinning sails, celebrating the country's rich milling heritage. (Photo by Sylvia Lederer/Xinhua)

People visit the De Valk windmill in Leiden, the Netherlands, on May 9, 2026. Dutch National Mill Day is celebrated annually on the second weekend of May, when windmills and watermills across the Netherlands open to the public. Visitors can enjoy guided tours, live demonstrations, and spinning sails, celebrating the country's rich milling heritage. (Photo by Sylvia Lederer/Xinhua)

Visitors view exhibits at the De Valk windmill in Leiden, the Netherlands, on May 9, 2026. Dutch National Mill Day is celebrated annually on the second weekend of May, when windmills and watermills across the Netherlands open to the public. Visitors can enjoy guided tours, live demonstrations, and spinning sails, celebrating the country's rich milling heritage. (Photo by Sylvia Lederer/Xinhua)