Underground forest (also called Crater Forest) is located inside the remote mountains in the southeast slope of Zhangguangcai Mountains. It is about 1000 meters above the sea level and it is the national nature reserve. When you walk along with the mountain road, many large craters will pop up before you as you ascending at the top of volcanoes. There are 10 craters with diameter of 400 meters to 550 meters and depth of 100 meters to 200 meters on the narrow and long belt which is 40 kilometers long and 5 kilometers wide. Among these craters, the No. 3 crater is the biggest one with its diameter of 550 meters and depth of 200 meters. Standing on the top of the crater and looking downwards, you will see luxuriantly green forest on the abrupt wall inside of the crater. The underground forest contains abundant resources such as rare timber and medicinal herb. Meanwhile, there is no lack of beastie. When you descend along the stairs, you can even see the rare green sheep appear and disappear. So the forest may also be rated as Underground Zoo. As you descend to the end of the stairs or the bottom of the crater, you can feel that the air temperature is abnormal in the karst cave, having thin ice in summer and clear spring in severe winter, peculiar enough. The deeper you go, the colder you will feel. At the end you may feel you are in an ice house.