The windmills at Kinderdijk are a group of 19 monumental windmills in the Alblasserwaard polder, in the province of South Holland, Netherlands. Most of the mills are part of the village of Kinderdijk in the municipality of Molenwaard, and one mill, De Blokker, is part of the municipality of Alblasserdam. Built in 1738 and 1740, to keep water out of the polder, it is the largest concentration of old windmills in the Netherlands and one of the best-known Dutch tourist sites. The mills are listed as national monuments and the entire area is a protected village view since 1993. They have been a UNESCO World Heritage Site since 1997.