Yellowstone National Park is a famous zone in the United States where wildlife thrives in an idyllic surrounding. The land is scattered with geysers and thermal sources, the scenery is truly phenomenal. These special attributes are due to a very unique condition : the park sits on top of a volcano caldera. In this case, it is a 640 000 years old volcano which has been inactive for thousands of year, leading to the return of nature atop the valley. Nowadays, people gather in great numbers each year to explore the wonders of Yellowstone National Park.