People walking across a boardwalk in the Porcelain Basin area of the Norris Geyser Basin in Yellowstone NP. The Norris Geyser Basin is the hottest and most changeable thermal area in Yellowstone. Explore the 2 1/4 miles (3.6 km) of trails and discover the location of the world's tallest active geyser, colorful hot springs, and microscopic life in one of the most extreme environments on earth.