Grand Prismatic Spring is the largest and most photographed hot springs in Yellowstone. It can be viewed at ground-level from the Midway Geyser Basin Trail or viewed from above from the Grand Prismatic Spring Overlook Trail starting at Fairy Falls Trailhead.
The Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the United States, and the third largest in the world, after Frying Pan Lake in New Zealand and Boiling Lake in Dominica. It is located in the Midway Geyser Basin.
Grand Prismatic Spring was noted by geologists working in the Hayden Geological Survey of 1871, and named by them for its striking coloration. Its colors match the rainbow dispersion of white light by an optical prism: red, orange, yellow, green, and blue.