Las Médulas, Spain, location of one enormous fracking head. The Romans devised a method of extracting minerals by diverting rivers into escarpments. The force of the water eroded away the base of the escarpment until large sections crashed down. In the case of Las Médulas, the whole mountain was removed leaving a collection of small hills in its place. Many of the hills have spectacular tunnels. Las Médulas was Eldorado, the gold was extracted and the Romans moved on to Segovia.
Segovia ‘lapis specularis’
The Romans had an insatiable appetite for gold and silver but another mineral ‘lapis specularis’ was also in demand and they mined it using the same hydraulic fracturing techniques they had used in Las Médulas. Lapis specularis is a crystal that they used to create small window panes, not sheet glass but a composite of crystals glued together. These were a boon to Roman baths and were used to make overhead skylights that helped heat the interior. The Roman fracking head is just outside present day Segovia.