Our planet's underground world is our new frontier... it's full of potential, but harnessing it is difficult, and often very dangerous. Despite the risks, humans have been exploring the benefits of going underground for thousands of years. See the secret that kept the ancient, wealthy city of Petra at the center of trade routes for hundreds of years. Learn how the Italian city of Orvieto survived sieges. Marvel at Istanbul's ingenious cisterns, some as big as cathedrals. Discover how everyday life in cities was transformed by tunneling deep beneath their inhabitants. Be there as a great tunnel is constructed underneath the Swiss Alps, testing human ingenuity to the maximum. Elegant ancient underground waterways, mining for spectacular natural treasures, amazing underground rescues, uncovering the secrets of the Universe... all this and more in the Mastering the Underground World volume of Amazing Underground Secrets.
