Nestling in the foothills of the Alps in northern Italy, 30 miles from the ancient city of Turin, lies the valley of Valchiusella. Peppered with medieval villages, the hillside scenery is certainly picturesque. But it is deep underground, buried into the ancient rock, that the region's greatest wonders are concealed. Here, 100ft down and hidden from public view, lies an astonishing secret - one that has drawn comparisons with the fabled city of Atlantis and has been dubbed 'the Eighth Wonder of the World' by the Italian government. For weaving their way underneath the hillside are nine ornate temples, on...