Its a (very) old watermill that could at one point have also been part of a sluice but I think it was actually used to mill grain at some point. I don't believe this is where it was originally used. Its more of a prop now but depending on the time of the year they used to still lower it into the water so you could watch it in action even if it was not hooked up to anything. Lots of people like to toss coins into the little box area, they really should not. Its bad for the water quality if they miss but what are you going to do?