A watermill is a facility where the power of water is harnessed to run an industrial process such as grinding grain, fulling wool, or spinning textiles. Watermills have been used historically in many regions of the world for a wide assortment of tasks, and they continue to be in active use in some areas. It is also possible to visit restored watermills, which are kept in good condition because they are objects of historical interest; such mills are sometimes used in demonstrations to show people how they would have worked.
Obviously, a watermill must be located near a source of water to generate energy. The watermill is built either right next to or over the water, with a water wheel or turbine of some form suspended in the water. As the water moves through the water wheel, it pushes it in a circular motion, moving gears inside the watermill which can be used to execute various tasks. The basic concept of the watermill appears to be at least 2,000 years old, as numerous examples from China, Ancient Greece, and the Middle East indicate.
One classic use of a watermill is in grinding grain into flour, with the use of a large millstone. Watermills can also be used in lumber production, to process various metals, and to run a variety of other tasks. With the use of a watermill, people could vastly increase industrial efficiency, producing a large volume of material at once. Without a watermill, people would have had to use human or animal labor to perform the same tasks, and this would have eaten up a great deal of time.
Because watermills would have been expensive to construct and maintain, they were typically made available to all of the residents of a surrounding area, who could utilize the watermill for a fee; by keeping the use open, the operator could ensure that the watermill would stay profitable. In some cases, the fee would be taken in barter; a flour miller, for example, might take a set percentage of the flour ground by the customers, re-selling the flour to fund the upkeep of the mill. Watermills were also historically among the first of the structures installed at a new site in heavily timbered areas, allowing people to process timber into lumber for construction.
Many people find watermills quite interesting to visit, and a number of antique examples have been converted into residences and hotels for this very reason. In these cases, the mill obviously is not functional, although the water wheel may be left in place because people find it interesting to watch.