Grand Prismatic Spring, in Yellowstone National Park’s Midway Geyser Basin, is the largest hot spring in the United States and Yellowstone and the third largest in the world. Known for its vivid bands of color, it has a deep blue center caused by water’s intrinsic color, while green, yellow, orange, and red edges come from thermophilic microbes in mineral-rich runoff. Early explorers recorded it in the 19th century, and geologists with the Hayden Geological Survey gave it its present name in 1871. About 370 feet wide and 160 feet deep, it releases roughly 560 U.S. gallons of 160 °F water each minute, making it one of Yellowstone’s defining geothermal landmarks.

Mammoth, Wyoming · USA