I love Yellowstone National Park. I have visited countries as far east as Japan, followed the footsteps of Romans, looked up at the Leaning Tower of Pisa, experienced volcanoes from afar and close up, and touched glaciers. Yet I return to Yellowstone again and again, gazing at waterfalls and lakes but especially at the vivid rainbow colors of many of the park’s hot springs, geysers, mud pots and fumaroles.