There are some strongholds built to protect the sacred, like an impenetrable wall, an intimidating fortress, or a mystical river. But there are others used for more sinister purposes. In this episode, we uncover the remarkable stories behind some of the world's most imposing structures.

Legendary beasts are believed to roam the earth and the seas, terrorizing, killing, and even possessing humans. But are these creatures merely metaphors or is there proof they've actually been unleashed to wreak havoc?