The air changes from climate-controlled and dry to cool and damp as I peer into a large pipe that extends from a 10-foot-wide hole in the brick wall. Although the centuries-old penstock no longer channels water from canals to turbines to power this former cotton mill, there’s still a shallow puddle at the bottom of the pipe.

Continued here:
The Impulsive Traveler: Getting a new perspective on gritty Manchester, N.H.