Large underground artificially mined holes, when found, was still quite shocked, it is said that the original water was submerged, and later found that there was a hole and the water was drained before finding several large holes, and there were obvious artificial excavation marks, so it quickly became a attraction. As for the ancients' efforts to dig the hole in the end, I can't know now, guessing it is not but the Tibetan soldiers' cave training field storage basement and the like, the ground is still quite spectacular, the stone walls neatly those horizontal lines should be antiquities.