Yesterday, Erin and I toured the Cambridge Water Works. It was pretty great. Tours are led by a fellow named Tim who is extremely personable and extremely passionate about water treatment. The place has a sense of humor, too (see the signs below).
One thing that astonished me was the fact that a watershed of only 25 square miles provides sufficient water for a city of 100,000 people – that's only a little over three times more area than the city itself. You wouldn't find anything like that in the West.