Abstract：An ancient man-made near ground surface rock cavern group was found in Longyou County，Zhejiang Province. The 24 large caverns were excavated 2000 years ago. Its findings attract the attentions of the scholars in the world. Through the field investigation it is found that there are many highlights involved in the excavation of these caverns，such as the inclined roof，the iron-shaped pillars，and the inclined sidewalls and etc.，in which the most noticeable is the inclined roof. In this paper，the detailed field investigation and 3D numerical analysis are carried out to show the engineering scientific problems contained in the inclined roof. The field investigation results reveal that the dip direction and dip angle of the roof are almost coincident with those of the bedding plane. That means the ancients knew very well how to control the direction and the dip angle of the cavern’s roof to sustain the stability of them. The results of the 3D numerical analysis also provide the same conclusion of that. The design of inclined roof can not only improve the stress condition of the surrounding rock but also reduce the settlement of the roof and the lateral deformation of the sidewalls. So，the inclined roof is the best way to solve the shallow buried problem.
