Lower Basin is the largest geyser basin of Yellowstone not only by area but also in terms of hot water discharge. Flat meadows, sparsely covered with groups of Lodgepole pines, are the typical landscape along Firehole River which flows through the basin's center.

Located between Madison Junction and Midway Geyser Basin, the Lower Basin comprises several different groups of thermal features within an area of approximately 11 square miles. Most widely known are the Fountain Group at Fountain Paint Pot and the Firehole Lake Drive with Great Fountain Group, White Creek Group, Pink Cone Group, White Dome Group, and Black Warrior Group. Close to Fountain Paint Pot are also Kaleidoscope Group, Sprinkler Group, and Thud Group. North of Thud Group and east of the roadway adjoin Quagmire Group, Culex Basin, Morning Mist Group, and Morning Mist Springs. A little bit farther north, Fountain Flat Drive gives access to River Group, Sentinel Meadow Group, Fairy Meadows Group, Fairy Creek Group, and Imperial Group.