Kinderdijk, Netherlands

Nineteen mills built around 1740 to drain the Alblasserwaard polder, and the largest concentration of old windmills in the country. They worked in stages, each lifting water a few metres into a higher basin until it could be discharged into the river — a mechanical staircase for a landscape that sits below sea level and would otherwise flood. They stayed in service into the twentieth century and are a UNESCO World Heritage site.