We went to look at a house for sale because the advert mentioned in passing that the place has a mill. I was intrigued, not least because there isn't much in the way of a river nearby. It turns out that a small stream that rises in a spring some 2 kilometres away passes near the house, where it forms a lake before running off into the fields. There is a mill wheel in a shed a short distance away, and it takes the water from the lake until, presumably, the lake is empty.
There is no longer any water passage from the lake to the mill, and the wheel is in disrepair. The wheel takes water in at the top, turning so as to release it at the bottom, which is a more efficient use of the water's energy than the usual type of mill where the water runs underneath the wheel. The wheel itself is about 7 metres in diameter.
Here's some pictures of the mill wheel and what's left of the mechanism.
Other aspects of the property were interesting: the water comes from a well, so it doesn't cost anything, except the annual analysis that is required since the water is drunk by farm animals (not required if the water is used solely by humans), and the owner owns a lot of hedges, so the wood-fired boiler is also free to run. He has to pay for electricity but I wonder if the mill could be used to get that for free as well. Possibly with solar panels as an adjunct. Hmmmm.