Grand Geyser is the tallest predictable geyser in the world, its water reaching heights of 150 - 200 feet every 6 - 7 hours on the dot.
Word to the wise: one YouTube commenter has a tip: "The secret to Grand Geyser is that the second eruption, 3 - 5 minutes after first eruption, is the far better show."
So named because gradual accretions of mineral deposits have built the geyser's cone into something like a tower, the Castle Geyser was named in 1870 when the Washburn-Langford-Doane Expedition, the same group who gave Old Faithful her name, reached the Upper Geyser Basin.
Great Fountain Geyser
The Great Fountain Geyser, located in the Firehole Lake area of Yellowstone Park, is the only semi-predictable geyser in the area, which means that Yellowstone issues predictions of when it is likely to erupt. White Dome Geyser, visible from the same area, erupts more often but less spectacularly, since the Great Fountain reaches heights of up to 200 feet, which makes it pretty amazing.
Steamboat geyser is a big ol' gal, the tallest, largest geyser in the world, regularly throwing sprays of boiling water 300 feet into the air. It is, however, one of the least predictable. It's major eruptions can be from anywhere between 3 days and 50 years apart.
The good news? It's been more active since 2018, meaning you have a better chance of seeing it. The bad news? That might mean that Yellowstone could go off at any second, wiping most of the West off the map and blackening the skies worldwide for months and months. It's a give and take, I guess.