Steamboat, at Norris, is the world's tallest geyser and has infrequent, unpredictable eruptions reaching 400 feet.
In the Old Faithful area, Grotto Geyser's fantastic bulbous shape is believed to be a result of geyserite covering the trunks of trees that had once grew there.
The West Thumb Geyser Basin is interesting indeed, although not as large or active as the Old Faithful area. Still, the beutiful lake in the background makes it a must stop.
Also in the Old Faithful area, Castle geyser is so named because, well, it looks like the tower of a castle.
West Thumb is so called because the inlet resembles a thumb of the greater Yellowstone Lake. Many mudpots and fumaroles are found here, accompanied by the pungent sulfurous odor.
This view is from the front of Old Faithful Inn early in the morning. In the distance the steam raises from several geisers and fumeroles.