Grand Prismatic Spring, in Yellowstone's Midway Geyser Basin, is the largest hot spring in the United States and the third-largest in the world, measuring roughly 200-330 feet (60-100 m) across and more than 121 feet (37 m) deep. Its rainbow-like bands of deep blue at the center shifting to green, yellow, and orange toward the edges come from heat-loving microorganisms (thermophiles) that thrive at different temperatures, making it one of Yellowstone's signature sights. As of summer 2026 no timed-entry reservation is needed — a standard park pass is enough — but the small Midway Geyser Basin parking lot fills up almost all day, so plan an early-morning or evening visit and pair it with the nearby overlook trail for the best view.
The blue-to-green-to-yellow-to-orange color gradient ringing the spring, seen from the boardwalk
How the colors shift with time of day and steam cover — early mornings or overcast periods can obscure the view
The elevated view from the Grand Prismatic Overlook Trail, which shows the full color pattern far better than ground level
Excelsior Geyser Crater right next door, a massive steaming crater from a once-violent geyser
Linking the visit with the nearby Fairy Falls trail for a longer loop
Good to know
SafetyThe ground around the spring is a thin, fragile mineral crust (sinter) that can give way without warning; people have suffered severe burns or died after stepping off the boardwalk into scalding, near-boiling water. Stay on the designated boardwalk and trails at all times.
SafetyYellowstone is bear country — carry bear spray and know how to use it before you need it. Keep at least 100 yards (91 m) from bears and wolves, and 25 yards (23 m) from bison, elk, and other wildlife.
SeasonMost of the Grand Loop Road closes to wheeled vehicles from early November through mid-April; in 2026 the West Entrance, Old Faithful, and Canyon roads did not reopen until April 17. Weather can force closures at any time, so check the NPS website for current road status before you go.
RulesThe Midway Geyser Basin lot is small and routinely full between 10 a.m. and 6 p.m., with waits of 20-30 minutes reported in peak season; arrive early or late, or use the larger Fairy Falls parking area nearby.
RulesStarting January 1, 2026, non-US residents aged 16 and older (including Korean travelers) must pay an additional $100 nonresident surcharge on top of the standard entrance fee, unless entering with an annual pass or America the Beautiful Pass.
MannersNever touch or scratch the colorful microbial mats, throw objects such as coins into the springs, or run or push near the boardwalk edge; keep children within arm's reach at all times.
CautionSearch ads for "Yellowstone reservations" or entrance passes often lead to third-party resellers that mark up official fees; buy passes only through nps.gov or recreation.gov.
Practical info
The closest airports are Bozeman Yellowstone International (BZN), with seasonal summer service also available at West Yellowstone Airport (WYS); most visitors rent a car and drive in through the West Entrance to reach Midway Geyser Basin. Entrance fees, parking conditions, and seasonal road openings change often, so confirm the latest details on the official NPS website before your trip.
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