Stumbled across this while mooching around after a maintenance trip to Sodor no More.
The water would have been fed from higher on the hill above, and the turning power of the wheel used to maybe crush olives, grind flour, or some other process? Can't find any info online about the place, so I'm just surmising.
There's another one in the area somewhere, researching... watch this space!
Cache is a magnetic micro, painted to match it's environment. Nothing in it except for a log. Only likely muggles are in the house opposite. This cache was in place for two months before publishing so proves that, if found and replaced with caution, it can stay muggle free.