One of the most interesting aspects of the history on the hill is coal mining. We know Swansea is based on the coal industry (Copper comes along MUCH later!). the earliest record of coal industry in Swansea comes from 1400 when a deep mine was being dug with all the necessary exenditure on drainage and candles for lighting and picks and shovels, so we can guess it was quite a substantial coal mine.
But the reality is that it was probably in Foxhole on the east side rather than in the town of Swansea. Foxhole has a thousand years of coal mining history!
The full story is in the first Cilfai book on the Historical Geography of the hill.
Cilfái: Historical Geography on Kilvey Hill, Swansea (lulu.com)
Below is what a coal mining adit looks like after a century of plant growth and recovery. This one is above Foxhole!
Nigel Robins 