inderdijk, located 15 miles east of Rotterdam, is a UNESCO-listed site that boasts 19 pristinely preserved windmills. The windmills were erected in the 1600s to drain the Alblasserwaard polders, which had suffered floods since the 13th century. One such flood, the Saint Elizabeth Flood of 1421, is both the source of the name Kinderdijk and of the associated fairy tale, "The Cat and the Cradle": after the storm, a wooden cradle was spotted on the flood waters, in which a cat jumped to and fro to keep the cradle afloat. When the cradle approached the dry land of the dyke, the locals discovered a baby inside -- hence the name Kinderdijk, Dutch for "children's dyke".
Nowadays the windmills have been relieved by more efficient screw pumps, but you can still visit the monumental 17th-century windmills that comprise the incredible man-made landscape of Kinderdijk. Views of the landscape are free; admission fees apply only to the visitors' windmill and special tours.