The Grand Prismatic Spring in Yellowstone National Park's Midway Geyser Basin is considered to be the largest hot spring in North America and third largest in the world. The 250 x 380 foot spring with temperatures ranging from 147 to 188 degrees fahrenheit, sits upon a wide, spreading mound where water flows evenly on all sides forming a series of small, stair-step terraces. The spring discharges an estimated 560 gallons of water per minute.