This group of 19 windmills is located in the village of Kinderdijk in South Holland, at the confluence of the Lek and Noord rivers. Built in 1738 and 1740 to rid excess water from the soil when the river rose, it is the largest collection of old windmills in the Netherlands. The mills themselves are national monuments and have been a UNESCO World Heritage Site since 1997. Some of the windmills are still used, though the main waterworks today are provided by two nearby pumping stations.