Years ago, when we lived in the Piedmont Triad of North Carolina (High Point, NC), we frequented the Old Mill of Guilford. Drive out past the Greensboro Airport, away from the nouveau riche South of that part of Greensboro/ High Point, and step back into rural North Carolina. The highway goes down to two lanes and, at bottom of a hill, turn right into history.
First built 500 feet upstream in 1767, it has just about continuously been a functioning water-powered gristmill and is still operating. No fancy museum here: the real deal with flour dust, and the wear and tear, of a working gristmill. It feels old and, walking through, you know a lot of hard work occurred around you.
There is a small shop off to the side selling the results (accompanied by a few touristy knick-knacks). We used to visit regularly; Ruth shopped, usually with me wandering around with a camera.
We went back last weekend, after perhaps 15-20 years, and found it virtually unchanged. Ruth and Mom shopped, I wandered. Amazing.