There is only one key word for Arxan – natural. For example, the unusual landform formed by volcanic lava is natural. Sitanglin is a representative scenic spot of this landform, and it's also one of the most spectacular views in the entire Daxinganling area. This forest area, stretching 20 kilometers long, is a geological heritage site. It was formed through solidification when lava erupted from flowing volcanoes and cooled down. Basalt landforms, soil, vegetation and organisms are all preserved in their natural state. Besides basalt, Tianchi (Heavenly Lake) in the Tianchi Mountains is also natural. This lake has a mythical name – Heavenly Mirror Lake. The lake is a kind of high-altitude crater lake formed from water accumulation after the eruption. The locals told us about a strange phenomenon, that there are no fish in this lake. Even if you put a fish in it, the fish will die. So far, it's still a mystery.