Grand Prismatic Spring, located in Yellowstone’s Midway Geyser Basin, is the largest hot spring in the U.S. and the third largest in the world. Spanning 370 feet in diameter and plunging 121 feet deep, its vivid hues—blue, yellow, orange, and red—are caused by heat-loving microorganisms (thermophiles) thriving in varying temperature zones. The clear blue center, at 160°F to 190°F, is too hot for most life. Powered by Yellowstone’s volcanic system, it discharges over 500 gallons of water per minute. Visitors can explore it via boardwalks or enjoy panoramic views from the Grand Prismatic Overlook Trail. A natural and scientific marvel, it is one of Yellowstone’s most iconic geothermal features.