Travel Rankings & Advice

Grand Prismatic Spring free

Grand Loop Road | Yellowstone National Park, Wyoming, United States | Official website
Grand Prismatic Spring Photo info
  • Type: Natural Wonders, Sightseeing
  • Time to Spend: 1 to 2 hours
Overall Rating: 4.5 (4.6)
Value: 5.0 (5.0)
Facilities: 0.0 (N/A)
Atmosphere: 4.5 (4.5)
About these ratings

If you're looking for a bit of artistic inspiration, you'll find it at the Grand Prismatic Spring. Sitting in the Midway Geyser Basin, this is the largest hot spring in the United States, approximately 250 by 300 feet in size and around 160-feet deep. But it's Grand Prisimatic's rainbow waters that really make it fascinating: While the center of the pool's deep cerulean hue is pretty characteristic, the deep reds, bright yellows and fiery oranges encircling the edges are not. These colors are 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 of the spring is too hot to support life — which is then reflected when light hits the organisms.  

The Grand Prismatic Spring sits just south of the Lower Geyser Basin along the Grand Loop. Other nearby attractions worth checking out include the Excelsior Geyser and the Turquoise Pool. Like the Lower Geyser Basin, the closest facilities are located several miles south. You'll find the Grand Prismatic Spring approximately 7 miles north of Old Faithful.

Check the National Park Service's Old Faithful Area page for more information about nearby services and facilities, comprehensive maps of points of interest, a list of ranger-led programs and operating hours.

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