The first big attraction we visited was Grand Prismatic Springs. Absolutely amazing. The photographs strike me as more beautiful than I remember it being in person. Nonetheless, it was a fascinating geothermal feature to witness.
Grand Prismatic Springs is the largest hot spring in the United States and the third largest in the world. The colors are caused by the mineral rich water and the pigmented bacteria that live there and each color represents a different temperature ring, the hottest being the blue at the very center.