In old Europe we dug a lot of such old wells from hill tops down to the ground water level during the middle ages. Actually prisoners of war dug most of them. Hundred of meters usually. It secured water from being poisoned with dead animals, the usual tactics then.

Hills in town centers were fortified to withstand longer sieges and rescue the town folks. Famous is eg. the well at the Königstein castle near Dresden, which was never conquered, with a depth of 152 metres. Such wells needed decades to be built. https://en.wikipedia.org/wiki/Castle_well