During a weekend trip to Glenwood Springs, Colorado, I stood at the edge of the natural spring pool. I could smell the wet concrete. I could almost feel the fresh water on my skin—cool in this pool, warm in the neighboring one. Across the water, chairs lined up like flamingos, and the resort's red roof and red flowers blended in with the mountain's red rocks. I was almost transported to another time, half-expecting to see ladies in one-piece suits and wide-brimmed hats lounging in the chairs or soaking their feet.