In 1992, a Chinese farmer in Longyou county, Zhejiang province, stumbled upon a remarkable underground discovery while draining water from a pond in the village of Shiyan Beicun. What he uncovered was an enormous network of artificial caves, covering about 30,000 square meters. The site includes 36 individual caves, each roughly the size of a large sports hall, with ceilings as high as 30 meters. To create these caves, an estimated one million cubic meters of rock were removed—equivalent to the volume of several hundred Olympic-sized swimming pools. The caves were initially thought to be natural formations, such as karst structures, which are common in limestone areas and form through water erosion over time. However, the discovery of straight walls, sharp angles, and a highly organized layout strongly suggested human involvement. Inside each cave, the walls are lined with parallel carvings made in a uniform pattern, indicating the use of standardized tools and a methodical approach to construction. Dating of the caves suggests they were built at least 2,000 years ago, yet they are not mentioned in any known historical records. Longyou county itself has a documented history spanning over two millennia, which raises questions about how such a massive and complex construction project could have been entirely forgotten. The location of the removed rock is also a mystery, as no traces of the material have been found in the surrounding area. Experts from various fields, including archaeology, engineering, and geology, have studied the caves extensively. However, no definitive consensus has been reached about the scale of the project or its original purpose. The uniformity of the carvings suggests a level of organization and technical skill that challenges traditional views of ancient societies. Despite the wealth of information gathered, the origins and function of the Longyou caves remain unsolved mysteries, with no historical documents or geological evidence offering a clear explanation of who built them or why.