Yasmin Mund climbed to the top of her Varanasi, India, guesthouse to see the sun rise over the Ganges River, but when she reached the roof, it was another, unexpected scene that caught her by surprise. “I looked over the right-hand side of the balcony, and my jaw dropped with disbelief,” she says. “Below were families—mothers, fathers, children, brothers, sisters, and dogs—all sleeping on the tops of their houses. It was midsummer … and sleeping san...