Place · 0.1 mi away
Overview
Grand Prismatic Spring is the showstopper of Midway Geyser Basin, about 7 miles from Old Faithful. It’s the largest hot spring in the United States (and among the largest on Earth), famous for an intense blue center and vivid rings of color.
Why the colors are so wild
The deep blue center is super‑hot, clear water that scatters blue light. Around the cooler edges, heat‑loving microbes build colorful mats—orange and red tones tend to dominate in summer, while winter mats skew greener. Together they create that unmistakable “living rainbow.”
Scale and stats
This pool is roughly 370 feet across and about 160 feet deep. It discharges on the order of 560 gallons per minute at around 160°F—serious heat you do not want to underestimate.
Getting the best view
The boardwalk puts you right beside the spring, where you can study the textures and color bands up close. For the classic top‑down perspective, hike to the Grand Prismatic Overlook from the Fairy Falls trailhead: about 1.5 miles round‑trip with ~200 feet of gentle gain.
Planning your visit
Parking at Midway Geyser Basin is limited and often packed from 10 am to 6 pm. The boardwalk is a flat, easy stroll; plan roughly an hour to see the spring and nearby features. If you add the overlook, budget 2–2.5 hours depending on crowds and photo stops.
Safety and wildlife
Stay on the boardwalks—thermal ground is thin and the water can cause severe burns. Supervise kids, secure loose items (wind is common), and give all wildlife plenty of space. Expect animals anywhere in the basin.
Brief history
Early trappers noted a “boiling lake” here in 1839. In 1871, the Hayden Geological Survey named it “Grand Prismatic” for its prism‑like colors.
Best time to visit
- For color: Bright midday light pops the mats; in cool mornings, steam often cloaks the spring.
- For fewer people: Aim for before 10 am or after 6 pm to sidestep peak parking congestion.
- Photographers: Pair a midday boardwalk lap (color detail) with the overlook for the aerial composition.
Pros
- Iconic rainbow-colored hot spring; largest in the U.S.
- Easy boardwalk access with close-up views
- Nearby overlook offers top‑down photography angles via a short hike
Cons
- Parking often fills 10 am–6 pm; congestion is common
- Morning steam can obscure views in cool conditions
Tips
- Arrive before 10 am or after 6 pm to avoid the worst parking crunch.
- For the most vivid colors, target bright midday; cool mornings can be steamy.
- Pair the boardwalk with the Grand Prismatic Overlook (about 1.5 miles round‑trip, ~200 feet gain).
- Plan ~1 hour for the boardwalk alone; 2–2.5 hours with the overlook.
- Stay on boardwalks—thermal ground is thin and near‑boiling water can cause severe burns.
