[1] The painting shows two working undershot water mills, with the major one being half-timbered with a cob-facade construction, tie beams, and vertical plank gable.
This is characteristic of the water mills in the Bentheim area in Germany, to where Ruisdael had travelled in the early 1650s.
[2] Although other Western artists had depicted water mills before, Ruisdael was the first to make it the focal subject in a painting.
[3] Meindert Hobbema, Ruisdael's pupil, started working on the water mills subject in the 1660s.
[1] The Getty Museum calls it Two Watermills and an Open Sluice on their website, object number 82.PA.18.