Midway Geyser Basin Trail

Midway Geyser Basin Trail is a roughly 0.7-mile lollipop loop: a boardwalk approach to the basin, then a loop around Grand Prismatic Spring. It crosses the Firehole River to Excelsior Geyser, follows its runoff, circles Yellowstone’s largest hot spring, and returns past Opal and Turquoise pools. Route descriptions put the full walk at about 0.7 to 0.8 mile; allow 45 to 60 minutes with time to look around. This is the close-up, ground-level walk, not the separate Grand Prismatic Overlook hike.

From the parking area, take the wooden bridge over the Firehole. The boardwalk climbs gently beside colorful runoff toward Excelsior’s crater. Less than a quarter-mile in, you reach the spring loop; either direction works. The return swings past Opal and Turquoise pools, then retraces the Excelsior approach and bridge. Once you’re on the basin boardwalk, there are no tricky choices or route-finding problems.

Use the Midway Geyser Basin lot on Grand Loop Road; parking is limited, especially from 10 a.m. to 6 p.m. Accessible parking, boardwalk and restrooms are available at the basin. Food or water service on the walk wasn’t found. Hydrothermal water can severely burn, so stay on the boardwalk and keep children close. Pets, including carried pets, aren’t allowed on boardwalks or trails; trained service animals are allowed. For a view down over the spring, use the separate Grand Prismatic Overlook trail from Fairy Falls parking.

Grand Prismatic is about 200 to 330 feet across and more than 121 feet deep. From the boardwalk you can see its blue center and colored rim up close, but you won’t get the broad overhead view from this route. Steam can drift across the pool and hide its far edge, so expect the scene to change as you move around it. The best photo is from the boardwalk with some of the orange and rust-colored mats in the frame; don’t step off for a clearer angle.

Excelsior’s jagged crater is roughly 200 by 300 feet and continually sends more than 4,000 gallons of water per minute into the Firehole River. The boardwalk follows its runoff, where channels spread across the pale ground and microbial mats add bands of color before the water reaches the river.

The orange, brown, green and yellow bands are linked to thermophiles, microscopic organisms that thrive in Yellowstone’s hot water. The hottest water supports colorless or yellow communities; cooler water supports orange, brown and green ones. The shifting bands make the runoff channels and spring margins worth a second look, even when steam softens the view across the pool.