Sounds seem louder.

The awareness of being underground, enclosed by stone, miles from exit, is constant.

The consequences of a torch failure are vivid to anyone who thinks about them for more than a moment.

The ancient miners went into this environment, deliberately, repeatedly, for centuries.

They went as trained and experienced underground workers who knew what they were doing and who had been prepared, by their communities, for exactly this kind of activity.

The experience was not novel to them — they had done it before, had returned from it before, had processed it in whatever cultural frameworks their communities provided for making sense of the underground.