The mineshaft was heavily surrounded by guards—not to stop people from entering, but to prevent people from escaping.
…After knowing what this place was, who would run in on their own accord? Every day, many people were detained and escorted here, temporarily staying here; after the previous group of miners died, the new bunch would obviously be sent down.
Those who refused to go down? Immediately beheaded!
Under the heavy pressure, even if they could only live for a few days, many people wanted to bet their luck—maybe they would be an exception and not die?
To prevent the escape of the miners who temporarily lived here, a tall wall was erected, piled up from heavy rocks; it definitely couldn't be dug through by normal people. It was like the great wall, reaching sixty five meters, and just as hard to leap over.
Moreover, guards patrolled underneath the tall wall; escaping was as hard as climbing the skies.