Photos by Pete McBride pedromcbride | I followed the remarkable Ganges River for 1,500 miles, from 18,000 feet atop the Gangotri Glacier in the Himalaya to the Bay of Bengal, for natgeo. On the 45-day expedition, my teammates Jake Norton and David Morton—both Everest guides—and I took water samples the entire way, measuring river health and pollutants for our film, Holy (un)Holy River. The results were both scary and inspiring. For more from the Ganges, follow pedromcbride.