是由石英砂岩构成的拱形门洞，在高达数十米、宽近百米，厚约8米的岩墙之中，有一宽16米，高约10米的天然石门横亘于登山道上，似鬼斧神工所凿。流水沿垂直节理裂隙侵蚀形成石墙，石墙中下部岩层厚度较薄，上部岩层厚度大且岩性较坚硬。由于外力因素作用，最初在石墙下部形成小型穿洞，后经风化、侵蚀和崩塌的改造，穿洞不断扩大而形成。In this quartz sandstone dyke which is tens of meters tall, almost a hundred meters wide and about 8m thick, there is a 16m wide and 10m tall natural arch cave. Water erosion along vertical joints formed a rock dyke, of which the middle and lower part was thinner and the upper part was thicker and harder. Exogenic forces caused a small hole in the lower part of the dyke, the weathering, erosion and collapse continuously expanded the hole and formed this arch cave.