Mammoth Hot Springs, Yellowstone National Park, WY
These springs and steam vents make it obvious that Yellowstone is like no place else. Here, hot water seeps up through underground limestone, and when this mineral-rich solution hits the air, it forms terraces of colorful travertine. About 50 such hot springs make this a truly surreal landscape, with spring water lacquering the terraced minerals. Summer crowds don’t typically arrive before 9 a.m., so make this your day’s first stop in order to stroll uncongested boardwalks.