Las Médulas is a historic gold mining site near the town of Ponferrada. It was the most important gold mine (and largest open pit gold mine) in the entire Roman Empire. Las Médulas Cultural Landscape is listed by the UNESCO as one of the World Heritage Sites.
The spectacular landscape of Las Médulas resulted from the ruina montium (wrecking of the mountains), a Roman mining technique described by Pliny the Elder in 77 AD. The technique employed was a type of hydraulic mining which involved undermining a mountain with large quantities of water. The water was supplied by interbasin transfer. At least seven long aqueducts tapped the streams of the La Cabrera district (where the rainfall in the mountains is relatively high) at a range of altitudes. The same aqueducts were used to wash the extensive alluvial gold deposits.
The area Hispania Tarraconensis was conquered in 25 BC by the emperor Augustus. Prior to the Roman conquest the indigenous inhabitants obtained gold from alluvial deposits. Large-scale production did not begin until the second half of the 1st century AD.References:
The Broch of Gurness is an Iron Age broch village. Settlement here began sometime between 500 and 200 BC. At the centre of the settlement is a stone tower or broch, which once probably reached a height of around 10 metres. Its interior is divided into sections by upright slabs. The tower features two skins of drystone walls, with stone-floored galleries in between. These are accessed by steps. Stone ledges suggest that there was once an upper storey with a timber floor. The roof would have been thatched, surrounded by a wall walk linked by stairs to the ground floor. The broch features two hearths and a subterranean stone cistern with steps leading down into it. It is thought to have some religious significance, relating to an Iron Age cult of the underground.
The remains of the central tower are up to 3.6 metres high, and the stone walls are up to 4.1 metres thick.