The Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the United States, and the third largest in the world
Located in the Midway Geyser Basin, the Grand Prismatic Spring is roughly 300 feet in diameter with water at a blistering-hot 160 degrees Fahrenheit. This beautiful natural attraction in Yellowstone is known – and named – for its dazzling array of colours that change throughout the seasons.
The water is a vibrant blue, with a red colour like lava surrounding it. However, what looks like lava is actually pigmented bacteria. They form microbial mats around the edge of the water. The bacteria are not all red though. It can range from green to red depending on the chlorophyll and carotenoids provided.
Boardwalks swirling in steam provide access to the spring. For the classic aerial view you need to take a short hike up the Fairy Falls trail.