Kinderdijk is in a polder at the confluence of the rivers Lek and Noord. To drain the polder, a system of 19 windmills was built around 1740. This group of mills is the largest concentration of old windmills in the Netherlands.
UNESCO, Power - Wind
The windmills of Kinderdijk are one of the best known Dutch tourist sites. They were placed on the list of UNESCO list of World Heritage Sites in 1997. --Wikipedia
Links: whc.unesco.org, www.kinderdijk.nl