Grain Mills are found in The Elder Scrolls V: Skyrim. They exist in several settlements, mostly on Farms or outside rural cottages. They can be used by the player. On use, the game enters the 3rd person view, and the player is shown moving the millstone in a circular motion for a few rotations.
The Grain Mill seems to serve no purpose other than showing the above animation. No object is put in the players inventory after using the Grain Mill. Manually dropping Wheat or other objects into the Grain Mill's grinding area has no effect as well.