Grand Prismatic Spring, Yellowstone National Park, Wyoming —
The largest hot spring in Yellowstone, Grand Prismatic Spring is about 300 feet (90 meters) across and 165 feet (50 meters) deep. At 188 degrees Fahrenheit, the bright blue water at the center of the pool is too hot to support life, but bacteria and algae thrive along the edges. The heat-loving bacteria produce orange, yellow and red pigments as a natural sunscreen, creating the spring's psychedelic look.