Whether or not you ever raved in a quarry, here’s one you’ll be raving about. Vienna’s St. Margarethen Quarry is a UNESCO World Heritage site and one of the oldest and most impressive in Europe. On this guided tour through its sandy limestone history you'll hear what ancient fossils have been discovered, how the stone helped to build and restore Vienna, and why the huge outdoor concert hall is one of the best venues in the world to experience opera.