Despite all of our modern technology and sophistication, there is much that we still don't know about what lies beneath our feet, deep underground. What is at the center of the Earth? Is there really a solid core of heavy metals, or could it be a hollow environment, as many researchers claim? And just how much of mankind's history took place underground? Recent discoveries of ancient underground structures such as the city of Derinkuyu and the Malta Hypogeum suggest that there may be more structures down there, waiting to be re-discovered. If much of our past was subterranean, could our future be as well?

Gold. It's one of the most valuable precious metals on the planet, has been coveted by societies for centuries, and can be found inside countless modern electronics. Mankind's quest for gold harkens back thousands of years, but what is the special power that gold wields over our collective consciousness? Is it merely because it's rare and valuable, or could it be something more than that?