Yellowstone Falls consist of two major waterfalls on the Yellowstone River, within Yellowstone National Park, Wyoming, United States. As the Yellowstone river flows north from Yellowstone Lake, it leaves the Hayden Valley and plunges first over Upper Yellowstone Falls and then a quarter mile (400 m) downstream over Lower Yellowstone Falls, at which point it then enters the Grand Canyon of the Yellowstone, which is up to 1,000 feet (304 m) deep.
On the picture, the lower falls which are 308 feet (94 m) high, or almost twice as high as Niagara.
The lower falls of the Yellowstone is still the largest volume major waterfall in the Rocky Mountains of the United States.
To give you an idea of the scale, you can see a platform on the right side where the falls start. The tiny little silhouets are people !!!