Grand Prismatic Spring Grand Prismatic Spring, also known as the Grand Rainbow Hot Spring, is the largest hot spring in the United States and the third largest in the world. With a diameter of over 100 meters, it displays different colors such as blue, green, yellow, orange, and red from the center outwards, making it the largest and most beautiful scenic spot in terms of area and color. It is impossible to see the panoramic view of the Grand Prismatic Spring from the peripheral trail. Viewing the prism up close is greatly affected by the constantly rising hot steam and wind, which greatly reduces the viewing effect. The best angle to see the prism is from above. To see the full view of this beautiful "Yellowstone eye", you have to climb the mountain behind the Prism Spring. Drive southeast along the highway, walk along the river road for about ten minutes, and you can see the prism emitting hot steam on your right hand side. On the left side of the mountain, there is a small path that many people have come out of, which is not very difficult. After climbing to the platform on the mountain for about ten minutes, you can see the panoramic view of the prism. There are trails in the Prism Spring scenic area, but it is not very clear to see because of the steam.