Although Yellowstone has very diverse landscapes (tall mountains, forests, canyons, rivers, lakes, waterfalls), the most famous of the park is the thermal features such as geyser, hot spring, and mud pool. And of all the geysers, Old Faithful is the best known. It erupts every couple of hours, almost precisely. One can check with the visitor center to find out the time (plus, minus ten minutes).
Not only the Old Faithful is impressive to watch, the area near it covers with all kinds of geysers and hot springs. Personally, I love Grand Geyser (which erupted several times a day, each time for more than ten minutes) and any pools with bright color (such as Belgian). I walked to every single geyser and hot spring I could find on the map. Once again, I was like a little girl lost in her favorite candy shore. 🙂
Blue Star Spring