This is absolutely my most favorite site in Yellowstone National Park. The Grand Prismatic Spring is the largest hot spring in the United State and the third largest in the world! The Prismatic is filled with extremely hot water that travels 121 feet from a crack in the earth to reach the surface. But there is more than just Prismatic. At the entrance a visitor passes by Excelsior Geysor, which at one time erupted to heights of 300 feet. It has had long periods of dormancy but erupted over two days in 1985. There are two smaller hot springs, Opal and Turquoise. Visitors walk on a boardwalk loop that lets them get up close to the thermal activity. From the boardwalk one can see the spring in parts, brilliant colors and pattern along with colorful steam. The colors change with light changes, wind and clouds. To see Prismatic Springs from above one must use the path that goes to Fairy Falls. This new half mile path was opened in 2017, climbs 105 feet and provides a safe fantastic view of the full Prismatic Spring.