Castle Geyser is located in the Upper Geyser Basin of Yellowstone National Park. The Castle Geyser eruptions typically last for 15 to 20 minutes and occur every 10-12 hours. During the eruption phase the hot water can reach a height of 90 feet which is then followed by a noisy steam phase lasting 30-40 minutes. The geyser is shown here while in the steam phase.

Looking like a medevieval fortress the 12 foot sinter was carbon-14 dated to around 1022 which is much younger than the previously presumed age of 5,000 to 15,000 years. The geyser was given the name "Castle Geyser" by Lieutenant G.C. Doane in 1870 because of its fortress like appearance.