[snip] The remains at Las Medulas and in surrounding areas show badland scenery on a gigantic scale owing to hydraulicking of the rich alluvial gold deposits. Las Medulas is now a UNESCO World Heritage site. The site shows the remains of at least seven large aqueducts of up to 30 miles in length feeding large supplies of water into the site. The gold-mining operations were described in vivid terms by Pliny the Elder in his Naturalis Historia published in the first century AD. Pliny was a procurator in Hispania Terraconensis in the 70’s and must have witnessed for himself the operations. The use of hushing has been confirmed by field survey and archaeology at Dolaucothi in South Wales, the only known Roman gold mine in Britain. [end]
http://en.wikipedia.org/wiki/Hydraulic_mining#Ancient_development
pic:
http://www.superstock.com/stock-photos-images/1566-0102674
another pic:
http://www.eyefetch.com/image.aspx?ID=447852
another wiki-wacky page:
http://en.wikipedia.org/wiki/Las_M%C3%A9dulas
(related) Roman Deep-Vein Mining:
http://www.unc.edu/~duncan/personal/roman_mining/deep-vein_mining.htm
and, the only known Roman gold mines in Britain:
http://en.wikipedia.org/wiki/Dolaucothi