Yellowstone's Midway Geyser Basin may be small, but it packs a big punch: In addition to Grand Prismatic Spring, see Excelsior Geyser, an enormous geyser crater, Turquoise Pool, and Opal Pool. You can get up close by strolling across the Firehole River and along the short boardwalk that snakes through the thermal area. Be sure to stay on the boardwalk. It is illegal and very dangerous to walk in the geyser basin.
The Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the United States, and the third largest in the world, after Frying Pan Lake in New Zealand and Boiling Lake in Dom..
