Vatican City is an inspirational place. You don't need to be Catholic or even religious to appreciate the architecture, art, and the city's historical significance.

But there is a place within the Vatican that's rarely seen. Hidden beneath the city is an underground fortress. Inaccessible to the public and protected by armed guards and state-of-the-art security. The Secret Apostolic Archives.

Within the stone and steel reinforced walls are vaults, climate controlled rooms and over 50 miles of shelves. And on those shelves are countless texts, relics and artificacts collected by the church for over a thousand years.

One of the most intriguing objects hidden in the archive is called the Chronovisor. A device that can view events anywhere and any time in history.

For years, its existence was just a rumor. No proof of the Chronovisor was ever found.

But a book released by a Vatican priest would change all that.

Let's find out why.