Yellowstone National Park
Yellowstone National Park has one of the world's largest petrified forests, trees which were long ago buried by ash and soil and transformed from wood to mineral materials. This ash and other volcanic debris are believed to have come from the park area itself as the central part of Yellowstone is the massive caldera of a supervolcano. The park contains 290 waterfalls of at least , the highest being the Lower Falls of the Yellowstone River at .
Hukou Waterfall
The Hukou Waterfall (), is the largest waterfall on the Yellow River, the second largest waterfall in China (after the Huangguoshu Waterfall in Guizhou), and the world's largest yellow waterfall. It is located at the intersection of the provinces of Shanxi and Shaanxi, to the west of Fenxi City, and to the east of Yichuan where the middle reaches of the Yellow River flow through Jinxia Grand Canyon. The width of the waterfall changes with the season, usually wide but increasing to during flood season. It has a height of over . When the Yellow River approaches the Hukou Mountain, blocked by mountains on both sides, its width is abruptly narrowed down to - . The water's velocity increases, and then plunges over a narrow opening on a cliff, forming a waterfall high and wide, as if water were pouring down from a huge teapot. Hence it gets the name "Hukou" (literally, "flask mouth") Waterfall.