Las Medulas is one of Spain's most extraordinary landscapes. In the 1st century AD, the Romans began mining gold here on an industrial scale, using a hydraulic technique called ruina montium that literally collapsed entire mountainsides. After two centuries of extraction they moved on, leaving behind a surreal terrain of red sandstone pinnacles, eroded cliffs, and chestnut forests that has been a UNESCO World Heritage Site since 1997.
The walking trails through the old workings are excellent. The viewpoint at Orellan gives you the full panorama of the red rock formations against green forest. It is a quiet place, well off the usual tourist circuits, and all the more rewarding for it.