Las Médulas remains of the most important gold mine in the Roman Empire. The spectacular landscape resulted from the ruina montium mining technique.
Ruina montium (Latin, "wrecking of mountains") was an ancient Romanmining technique described by Pliny the Elder (Natural History 33.21), who served as procurator in Spain.[1][2] It is thought to draw on the principle of Pascal's barrel.[3] Miners would excavate narrow cavities down into a mountain, whereby filling the cavities with water would cause pressures large enough to fragment thick rock walls.[4][5][6]
^Pliny the Elder (1857) with John Bostock and H.T. Riley, trans., The Natural History of Pliny (London, England: Henry G. Bohn), vol. 6, Book 33, Ch. 21, pp. 101–104.