For millennia, there has been speculation about how the world will end. From the detailed account in the Book of Revelation, to the prophecies foretold by Nostradamus, and even the belief in devastation caused by a strange blue star. Could any of these predictions come true? And if so, when?

Most of the world's holiest places sit in plain sight, able to be seen and experienced. But there are some hidden deep underground. The revered tomb of Jesus Christ, a secret Knights Templar tunnel, and a prehistoric temple in Malta with mystical properties--why were they concealed? And what mysteries have we unearthed in these subterranean sacred spaces?