As one early visitor described the Mammoth Hot Springs, "No human architect ever designed such intricate fountains as these. The water trickles over the edges from one to another, blending them together with the effect of a frozen waterfall." The hot springs were an early commercialized attraction for those seeking relief from ailments in the mineral waters. Today, to preserve these unique and fragile features, soaking in the hot springs is prohibitted. Mammoth Hot Springs are a surface expression of the deep magmatic forces at work in Yellowstone. Although these springs lie outside the Yellowstone Caldera boundary, scientists surmise that the heat from the hot springs comes from the same magmatic system that fuels other Yellowstone hydrothermal areas. A large fault system runs between Norris Geyser Basin and Mammoth, which may allow thermal water to flow between the two. Also, multiple basalt eruptions have occurred in this area. Thus, basalt may be a heat source for the Mammoth area.

The Mammoth Hot Springs Historic District has statewide significance as the administrative and concession headquarters of the largest national park in Wyoming. Park managers here developed significant conservation policies that greatly influenced the nascent National Park Service. It is also significant for its architecture, which includes Colonial Revival, Rustic, Prairie, Art Moderne, French Renaissance, and English Tudor styles. The district contains 189 buildings, 2 sites (Mammoth Hot Springs Campground and Fort Yellowstone Parade Ground), and 1 object (flagpole). Of these, 35 buildings also contribute to the significance of the overlapping Fort Yellowstone National Landmark, as does one structure (Fort Yellowstone Powerhouse) and one site (Fort Yellowstone Parade Ground). These remain from the 1890s and early 1900s when the US Army administered the park. They reflect the layout and architecture of a typical western army fort of the nineteenth century.

Lamar Valley is one of the nation's premier wildlife watching destinations! Elk, bison, deer, and pronghorn thrive in the grasslands of this area, known as the northern range. In fact, some of the largest wild herds of bison and elk in North America are found here. The northern range is critical winter habitat for these large animals, which in turn provide food for several packs of wolves. Coyotes are also common, and occasional bobcat, cougar, or red fox are reported.

The Grand Canyon of the Yellowstone is roughly 20 miles long, measured from the Upper Falls to the Tower Fall area. The canyon was formed by erosion as Yellowstone River flowed over progressively softer, less resistant rock. The 109-foot (33.2-m) Upper Falls is upstream of the Lower Falls and can be seen from the Brink of the Upper Falls Trail and from Upper Falls Viewpoints. The 308-foot (93.9-m) Lower Falls can be seen from Lookout Point, Red Rock Point, Artist Point, Brink of the Lower Falls Trail, and from various points on the South Rim Trail. The volume of water flowing over the falls can vary from 63,500 gallons (240,374 l)/second at peak runoff in the spring to 5,000 gallons (18,927 l)/second in the autumn.

he 109-foot (33.2-m) Upper Falls is upstream of the Lower Falls and can be seen from the Brink of the Upper Falls Trail and from Upper Falls Viewpoints. The 308-foot (93.9-m) Lower Falls can be seen from Lookout Point, Red Rock Point, Artist Point, Brink of the Lower Falls Trail, and from various points on the South Rim Trail. The volume of water flowing over the falls can vary from 63,500 gallons (240,374 l)/second at peak runoff in the spring to 5,000 gallons (18,927 l)/second in the autumn.

Hayden Valley is a great place to view wildlife. Grizzly bears may be seen in the spring and early summer preying upon newborn bison and elk calves. Bison are often seen in the spring all the way through the fall rut. Coyotes and foxes are often seen in the valley. Ducks, geese, and American white pelicans cruise the river, while a variety of shore birds may be seen in the mud flats at Alum Creek. Keep an eye out for bald eagles, northern harriers, and sandhill cranes.

Situated at 7,733 feet above sea level, Yellowstone Lake is the largest high elevation lake (above 7,000 feet) in North America. It is roughly 20 miles long and 14 miles wide, with 141 miles of shoreline and a surface area of 132 square miles . Yellowstone Lake freezes over completely every winter in late December or early January, with ice thicknesses varying from a few inches to more than two feet. The lake usually thaws in late May or early June. Yellowstone Lake remains cold year-round, with an average water temperature of 41°F. Yellowstone Lake has the largest population of wild cutthroat trout in North America. How a Pacific Ocean fish got to a lake that drains to the Atlantic puzzled experts for years. Scientists now believe that Yellowstone Lake once drained to the Pacific Ocean via the Snake River, and that fish swam across the Continental Divide at Two Ocean Pass.

Watching Old Faithful Geyser erupt is a Yellowstone National Park tradition. People from all over the world have journeyed here to watch this famous geyser. The park’s wildlife and scenery might be as well-known today, but it was the unique thermal features like Old Faithful Geyser that inspired the establishment of Yellowstone as the world’s first national park in 1872. Old Faithful is one of nearly 500 geysers in Yellowstone and one of six that park rangers currently predict. It is uncommon to be able to predict geyser eruptions with regularity and Old Faithful has lived up to its name, only lengthening the time between eruptions by about 30 minutes in the last 30 years. Thermal features change constantly and it is possible Old Faithful may stop erupting someday. Geysers and other thermal features are evidence of ongoing volcanic activity beneath the surface and change is part of this natural system.

The Old Faithful Inn was designed by Robert C. Reamer, who wanted the asymmetry of the building to reflect the chaos of nature. It was built during the winter of 1903–1904. The Old Faithful Inn is one of the few remaining log hotels in the United States. It is a masterpiece of rustic architecture in its stylized design and fine craftsmanship. Its influence on American architecture, particularly park architecture, was immeasurable. The building is a rustic log and wood-frame structure with gigantic proportions: nearly 700 feet (213 m) in length and seven stories high. The lobby of the hotel features a 65-foot (20-m) ceiling, a massive rhyolite fireplace, and railings made of contorted lodgepole pine. Stand in the lobby and look up at the exposed structure, or walk up a gnarled log staircase to one of the balconies. Wings were added to the hotel in 1915 and 1927, and today there are 327 rooms available to guests in this National Historic Landmark.

The Madison River, a tributary of the Missouri River, begins in Yellowstone National Park at the confluence of the Firehole and Gibbon rivers. This site is called Madison Junction. Both the Firehold and Gibbon rivers are thermally influenced by contributions from geothermal features. The Madison River travels 19 miles (31 km) through Yellowstone National Park before crossing the park boundary and flowing into Hebgen Lake towards Ennis, Montana. It continues northwest from there and meets the Jefferson and Gallatin rivers to form the Missouri River. The Madison River is a renowned recreation destination for fishing, birding, and wildlife viewing. There is a park legend which tells of explorers camping here in 1870 and deciding Yellowstone should be set aside as a national park. It is a wonderful story, but it isn’t true. Explorers did camp at the junction in 1870, but they apparently did not discuss the national park idea.

Grand Prismatic Spring, Yellowstone’s largest hot spring, is 200-330 feet in diameter and more than 121 feet deep. Hot springs are the most common hydrothermal features in Yellowstone. Their plumbing has no constrictions. Superheated water cools as it reaches the surface, sinks, and is replaced by hotter water from below. This circulation prevents water from reaching the temperature needed to set off an eruption. Hydrothermal features are also habitats in which microscopic organisms survive and thrive. They are called thermophiles: "thermo" for heat and "phile" for lover. Although they are too small to be seen with the naked eye, trillions are grouped together and appear as masses of color. They are nourished by energy and chemical building blocks. Colorless and yellow thermophiles grow in the hottest water. Orange, brown, and green thermophiles grow in cooler waters.

This 2-mile, one-way road off the Grand Loop south of Madison is pushed against the caldera walls, and provides great viewing opportunities for thew in addition to waterfalls, rapids, and wildlife.

Gibbon Falls drops 84 feet (25.6 m) over a remnant of the Yellowstone caldera rim. The caldera was created by a massive volcanic eruption approximately 631,000 years ago. The flow at the falls varies greatly throughout the year. During the spring snow-melt the Gibbon River caries much more water than it will later in the summer, and this season provides the most impressive views of the fallw, but because of weather and all the other variables this falls is always worth a look.

Sheepeater Cliff is made up of columnar basalt deposited by lava flows roughly 500,000 years ago. The Gardner River flows through the valley, exposing the flow and forming the cliff. The basalt of Sheepeater Cliff are known as columnar basalt due to the hexagonal fracture lines that formed in the basalt when it cooled. The cliffs are noted as a textbook example of a basaltic flow with well defined joints and hexagonal columns. They were named after a band of Eastern Shoshone known as Tukuaduka (sheep eaters). Many of the exposed cliffs are located along a steep inaccessible canyon cut by the Gardner near Bunsen Peak, but some of the cliffs located just off the Grand Loop Road can be reached by car.