The underground ancient city is more than ten stories deep from the ground, but now only two or three stories have been opened. I don't know whether to create a mysterious atmosphere or to protect the ancient city. The light inside is very dim. In some places, we have to turn on the lights of mobile phones to illuminate. The heat outside vanished from the moment I entered the old underground city. There was no summer heat in it. But while we were visiting, we were discussing whether it would be easy to get rheumatism if we lived in such a humid place. Underground ancient cities had opened doors with different functions, such as churches, schools, conference halls, cemeteries, isolation of patients, and ventilation holes that used to penetrate more than ten floors. Only when we came to this historic site with reasonable design and high difficulty in building, did we realize that it was only when Yu Gong moved mountains. It's a piece of cake.