In the 1st cen­tu­ry A.D. the Roman Impe­r­i­al author­i­ties began to exploit the gold deposits of this region in north-west Spain, using a tech­nique based on hydraulic pow­er. After two cen­turies of work­ing the deposits, the Romans with­drew, leav­ing a dev­as­tat­ed land­scape. Since there was no sub­se­quent indus­tri­al activ­i­ty, the dra­mat­ic traces of this remark­able ancient tech­nol­o­gy are vis­i­ble every­where as sheer faces in the moun­tain­sides and the vast areas of tail­ings, now used for agri­cul­ture.