Longyou Grottoes

Located in Longyou, Zhejiang, the Longyou Grottoes are a group of underground man-made caves and one of the most advanced underground man-made structures in ancient China. They are also a wonder of the world in terms of underground space development and utilization. The Longyou Grottoes can be traced back to 212 BC and are known locally as the "Ninth Wonder of the World." The Longyou Grottoes are located in a small mountain called "Tongtan Mountain" by the locals, 3 km north of the city. The mountain is only a few miles in circumference, but it contains 24 man-made caves of varying sizes and intricate layouts. Before they were discovered, they were all buried in water and soil, and the rock at the entrance of the caves had collapsed, so it was difficult to see them. The local government has now developed five of the caves for visitors to see. The shape and size of these caves are generally similar: the area of the cave halls ranges from a few hundred square meters to more than a thousand square meters; the height of the caves ranges from 20 to 40 meters; the entrances are rectangular; the walls are steep and the tops are arched; there are 2 to 5 large stone pillars in the caves, with cross-sections shaped like irons, and the largest ones require five people to hold them; the surfaces of the tops, walls, and stone pillars are all carved with fine diagonal patterns, resembling tiger stripes; there is a wide stone staircase from the entrance to the bottom of the cave, with a wavy shape; and there is one or two stone pools and artificial slopes at the bottom of each cave. A large number of experts and scholars have put forward various speculations and arguments about the age and use of the caves: quarries, tombs, military depots, ice storage, megalithic culture, Taoist paradises, and refuges for rebellious miners, among others. When the Longyou Grottoes were first discovered, they were thought to be an "abandoned quarry," so they did not cause a sensation and remained unknown for six years. It was not until 1998 that they attracted the attention of the public. Today, similar caves have been found scattered along the north bank of the Qujiang River, with at least 50 caves in an area of 2.88 square kilometers. It is hard to imagine how such a huge underground project could have been completed with the underdeveloped technology of ancient times. The mysteries of the caves make visitors "curious when they enter the caves and puzzled when they leave."