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. Old Faithful may be more famous, but the Grand Prismatic Hot Spring is the most photographed thermal feature in Yellowstone. That's because of its crazy-bright colors and enormous size. 

The hot spring has bright bands of orange, yellow, and green ring the deep blue waters in the spring. The Midway Geyser Basin's Grand Prismatic Spring is the largest hot spring in the United States, approximately 370 feet in size and around 121 feet deep. These multicolored appearance is caused by pigmented thermophilic bacteria that thrive on the rich minerals produced by the geothermic activity. The color of the bacteria is determined by the temperature of the water the center is too hot to support life which is then reflected when light hits the organisms.

This natural wonder is one of the park's most photographed sights, so expect crowds when you visit. You may find fewer visitors if you arrive early, but fog is common until late in the morning on cooler days, so travelers recommend arriving around 10 a.m. No matter when you go, visitors say the attraction's Fairy Falls overlook will provide you with the best views. Grand Prismatic Spring sits 2 miles southwest of the Lower Geyser Basin and 7 miles north of Old Faithful. Other nearby attractions include the Excelsior Geyser and the Turquoise Pool.