Castle Geyser is a large geyserite mound occurring within the Upper Geyser Basin of Yellowstone National Park. The feature
was named in allusion to the appearance of the sizeable geyserite build-up and terracing around the main vent. When Castle
geyser erupts, it is possible to see it from the entrance road to the Old Faithful Inn gas station, and pretty much anywhere
on Geyser Hill. However, the view from the other side of the Firehole River is pretty uncluttered. Sitting on the boardwalk
by Liberty Pool or the "Frog Pools" allows other features to be observed at the same time.