Yellowstone National Park is the first national park in USA which was established in 1872. This 3500 Square Miles (9000 Sq KM = 2.21Million Acres) park sits on an active volcano with a lot of hydro thermal areas and active geysers, hot springs, mud pots and steam vents.

Grand Prismatic Hot Spring is the most beautiful thermal feature in the park. It is similar to a rainbow of colors - bright bands of orange, yellow and green rings around the deep blue waters in the hot spring. The colors are due to different heat loving bacteria in the water. Top view of the Hot Spring from a nearby hill.