On the right of the photo: The original paddle wheel lock (1925, Art Nouveau style), built as a paddle wheel pumping station to pump water back into the higher-lying section of the Drentsche Hoofdvaart canal. This is because a large amount of water is lost to the lower section each time ships pass through the adjacent lock.
On the left of the photo: The modern pump house (1990), built as the active polder and reservoir pumping station. It has completely taken over the function of the old pumping station.

Rijksmonument (national monument)