It looks like an ancient fortress that might house a monster. But it’s actually the largest cone geyser in Yellowstone. Located in the Upper Geyser Basin, Castle Geyser wows with its artistic cone, eruptions, and post-eruption steaming.
Contrary to real life fortresses, Castle’s cone stands only 12 feet high. But its architecture took quite some time to construct. In fact, for sinter to build a cone of that size would take an estimated minimum of 5,000 years.
Often Castle Geyser spits and splashes. But when it erupts, boiling water shoots up to 90 feet in the air. The action can run for 20 minutes. Afterwards, Castle breaks into a rowdy session of fuming steam, puffing and belching for 40 minutes.
If you want to see Castle Geyser erupt, you’re in luck. You can catch these eruptions about every 11-12 hours or so. The National Park Service predicts eruptions for this geyser; find current predictions on Yellowstone’s Geyser app or in Old Faithful Visitor Education Center.
Find Castle Geyser on the paved walkway north of the visitor center. Consult the boardwalk maps for direction and location.