[The description of Spindle was provided by Steve Gryc.]
Unofficially-named "A-0" Geyser lies about a hundred feet southeast of the Surprise Pool parking area along the Firehole Lake Drive. You can view the geyser from the parking area or from the well-defined trail that heads southeast from the Great Fountain Geyser parking area. The name "A-0" comes from the geyser's proximity to A-1 and A-2 geysers, though its appearance is much different from the currently-inactive other two geysers. "A-0" can be identified by its well-defined, but shallow, round basin. In the center of the basin is a round vent, giving the geyser the appearance of a circle within a circle. No pool forms as water bursts from the vent to heights between 5 and 10 feet. During the 1999 Spring/Summer season intervals averaged around 24 minutes with durations averaging around 30 to 40 seconds. There is another very small, unnamed geyser between "A-0" and Botryoidal Spring which erupts about every 10 minutes from several small holes to a height of a few inches to two feet.