Introduction to Tongtian Cave: Tongtian Cave is a large cave under the Great Wall located on the hillside of Tiger Mountain. Tongtian Cave is divided into two small entrances on the left and right, much like the two nostrils of a cow. Between the two small cave entrances, there is a small raised ridge, which looks like the bridge of a cow's nose. Therefore, Tongtian Cave is also called Nose Cave. Legend has it that the Cowherd God ascended to heaven from here.