Introduction to Sim Fountain Basin: Sim Basin is located on the edge of Yellowstone Lake. It was formed due to the collapse of the earth's crust 150,000 years ago. When the hot fountain and the lake water combine, a wonderful smoky landscape appears: the Abyss Pool (Abyss Pool). Abyss Pool is the deepest hot spring pool in Yellowstone Park, reaching a depth of 16 meters. The water in the pool is dark green. Looking down from the trail beside the pool, it is bottomless. In addition, there are landscapes such as: Black Pool, Fishing Cone, Thumb Paint Posts, etc.