天宝山穿洞位于东平河西岸，天宝山景点入口左侧山上。穿洞洞体宏大，呈近正方形，边长约20米，是东兰国家地质公园范围内最大、保存最好的天然穿洞。穿洞顶部有停止发育的钟乳石景观，底部有崩塌堆积物及多种珍稀植物，不仅展示了大自然的奥妙，也在向人们传递着地质演化的重要信息。 Tianbaoshan karst cave, is located on the west coast of Donping river, lies on the left side of the mountain which situated the entrance to Tianbaoshan scenic spot. The karst cave body is huge, which is approximately in square, with a length of 20 meters.It is the largest and the most well preserved natural karst cave within Donglan National Geopark. There are stalactite landscape on the roof which has stopped development, and many collapse accumulation and a variety of rare plants in the bottom, which not only shows the wonders of nature, but also conveys important information about geological evolution.