Blue Orange Geothermal Basin, Yellowstone National Park

Easily explored on just a few miles of sturdy boardwalks, Norris Geyser Basin offers a concentrated dose of Yellowstone National Park's geothermal grandeur. Blue-water hot springs flush with bright bacterial mats match the intense tones of Grand Prismatic Spring, and most of the basin bubbles at 199 degrees Fahrenheit, the boiling point here at 7,500 feet. True to its name, the basin is pocked with geysers: Highlights include the acidic-as-vinegar Echinus Geyser and the tallest active geyser in the world, 300-foot Steamboat Geyser—twice as high as Old Faithful, but not half as famous due to its unpredictable schedule.