Grand Prismatic Spring

Grand Prismatic Spring is the largest hot spring in the United States and one of the most beautiful and surreal natural features on Earth, a vast, steaming pool in the Midway Geyser Basin of Yellowstone National Park whose brilliant rainbow colors have made it an iconic image of the world’s first national park. Some 370 feet across and over 120 feet deep, the great spring glows with a deep, clear blue at its scalding center, ringed by dazzling concentric bands of green, yellow, orange and fiery red that radiate outward across the surrounding terrace.

These extraordinary colors are created by life: heat-loving microorganisms (thermophilic bacteria and archaea) that thrive in the spring’s runoff at different temperatures, each producing its own pigment, painting the rings of color around the hot blue water. Best appreciated from above — from the overlook on the nearby hillside, or from the air — Grand Prismatic’s immense scale and astonishing colors create one of the most photographed and unforgettable scenes in Yellowstone. Vast, vivid and surreal, Grand Prismatic Spring is a treasured wonder of Yellowstone and the natural world.

Grand Prismatic Spring is experienced from the boardwalk that crosses the Midway Geyser Basin past the great spring (and the nearby Excelsior Geyser), and especially from the Grand Prismatic Overlook, reached by a trail on the nearby hillside (via the Fairy Falls trailhead), which offers the spectacular elevated view of the full rainbow of colors — the best way to appreciate the spring’s scale and beauty. Viewing and photographing the spring from the boardwalk and the overlook is the signature experience. The combination of the immense, vividly colored spring and the surrounding geyser basin makes Grand Prismatic a premier and unforgettable Yellowstone destination.

Midday on a clear, sunny day brings out the spring’s most brilliant colors (and the steam is thinnest when it is warmer and less windy), while early morning and cool days bring heavier steam that can obscure the view. Summer is the busy peak with full access; spring and fall offer fewer crowds. The overlook trail rewards the effort year-round (winter access is limited). Midday sun for the brightest colors, and the elevated overlook for the full rainbow, are the keys; visit on a clear, warm, calm day for the best view, and be patient with the steam.

Grand Prismatic Spring was named by the Hayden Expedition in 1871 for its beautiful, prismatic (rainbow) colors, helping to inspire the creation of Yellowstone as the world’s first national park the following year. The great spring, the largest in the country, has astonished visitors ever since with its scale and color. As understanding of the thermophilic microbes that create the colors grew, the spring became not only a scenic wonder but a window into extreme life. Grand Prismatic preserves and presents one of Yellowstone’s most iconic and beautiful features, a treasured symbol of the park’s geothermal wonders.

Grand Prismatic Spring is a vast hot spring powered by Yellowstone’s volcanic heat, where superheated water rises from deep underground to fill the great pool. The water is hottest (and clearest deep blue) at the center, where it emerges, and cools as it spreads outward across the terrace, creating concentric temperature zones. The deep blue of the center comes from the scattering of sunlight in the clear, deep, hot water, while the surrounding rings of color are created by the different thermophilic microbes living at each temperature. The volcanic heat, the rising water, and the temperature zones — painted by microbial life — create the surreal, colorful spring.

The Midway Geyser Basin and the surrounding forests and Firehole River around Grand Prismatic host the wildlife of Yellowstone — bison and elk that sometimes wander among the geothermal areas (keep your distance), along with the broader park’s wildlife in the nearby forests and river. Most remarkably, the spring itself teems with life invisible at a glance: the thermophilic microorganisms that create its colors. The runoff and the surrounding habitat support varied life. While visited for its beauty, Grand Prismatic is, in its colored rings, a vivid display of extreme microbial life, and the surrounding basin shares in Yellowstone’s rich wildlife.

Grand Prismatic Spring is a living wonder, its famous rainbow colors created by mats of thermophilic microorganisms — heat-loving bacteria and archaea — that thrive at different temperatures in the spring’s runoff, each community producing pigments (carotenoids and others) that paint the rings of orange, red, yellow and green. These extremophiles, thriving in scalding, mineral-rich water, are of great scientific interest and represent some of life’s extremes. The deep blue center is too hot even for them. Protecting the fragile spring and its microbial life — by keeping strictly to the boardwalks — sustains both the surreal beauty and the scientifically significant ecology of this iconic feature.

Grand Prismatic Spring, the largest hot spring in the United States and one of the most beautiful on Earth, holds a treasured place among America’s natural wonders and as an iconic image of Yellowstone, the world’s first national park. Its astonishing rainbow colors and immense scale have made it one of the most photographed and beloved features of the park, a symbol of Yellowstone’s geothermal marvels. Embodying both surreal natural beauty and the wonder of extreme life, Grand Prismatic Spring is a cherished icon of Yellowstone and a window into the colorful, living wonders of the natural world.

Grand Prismatic Spring is in the Midway Geyser Basin of Yellowstone National Park, in northwestern Wyoming, along the Grand Loop Road between Old Faithful and Madison, reached most easily from the West and South entrances. The Yellowstone entrance fee applies. The spring is viewed from the boardwalk in the Midway Geyser Basin (with its own parking) and, for the spectacular elevated view, from the Grand Prismatic Overlook reached by a trail from the nearby Fairy Falls trailhead. The boardwalks and trails are seasonal. Check the National Park Service for conditions and access before visiting.

The National Park Service protects Grand Prismatic Spring, the Midway Geyser Basin and their fragile geothermal features and microbial life within Yellowstone National Park. Visitors help by staying strictly on the boardwalks and the overlook trail (the thin crust and scalding water are deadly, and stepping off destroys the fragile microbial mats and features), never touching, entering or throwing anything into the spring, keeping a safe distance from wildlife, packing out everything, and following the rules. Protecting the spring and its thermophilic life — by keeping to the boardwalks and trail — sustains both the surreal beauty and the scientific value of this iconic feature.

At Grand Prismatic Spring, stay strictly on the boardwalks and the designated overlook trail — the ground around the spring is a thin, fragile crust over scalding water that has killed people who stepped off; never leave the boardwalk, touch the water, or enter the features. Keep a safe distance from bison or elk near the boardwalks (they are dangerous). The boardwalk can be slippery with steam and condensation; watch footing, and supervise children closely. The overlook trail is a moderate hike; carry water. Respect the deadly geothermal hazards and the wildlife above all.

The Yellowstone entrance fee applies. Stay strictly on the boardwalks and the overlook trail; do not step off, touch, enter, or throw anything into the spring or features. Keep required distances from wildlife; never approach or feed them. Do not collect anything. Pets are restricted (not allowed on boardwalks). Drones are prohibited. Pack out all trash. The boardwalks and trails are seasonal. Check the National Park Service for conditions and current rules before visiting; follow all Yellowstone regulations.

Grand Prismatic Spring lies in Yellowstone’s geyser country, with Old Faithful and the Upper Geyser Basin just to the south, the Lower Geyser Basin and the Firehole River nearby, and the broader wonders of Yellowstone — the canyon, the lake, the wildlife valleys — in the park, with Grand Teton to the south. The gateway towns of West Yellowstone and Jackson lie outside the park. The Greater Yellowstone Ecosystem defines the region. Grand Prismatic Spring anchors, with nearby Old Faithful, the geothermal heart of Yellowstone, a centerpiece of a visit to the world’s first national park.

See Grand Prismatic Spring from both the boardwalk (for a close-up of the steaming, colorful pool) and, for the spectacular full-rainbow view, from the Grand Prismatic Overlook reached by the trail from the Fairy Falls trailhead — the elevated view best reveals its scale and colors. Come at midday on a clear, warm, calm day for the brightest colors and the thinnest steam. Stay strictly on the boardwalks and trail (the crust and water are deadly), keep your distance from wildlife, and pair the spring with nearby Old Faithful and the rest of Yellowstone.