These days, the world often seems like a pretty small place. Thanks to the relative ease of international travel, real-time communication and the all-seeing eye of Google Earth, it sometimes feels like there isn't a lot of mystery left.

But it wasn't long ago that the planet was much larger and more mysterious. Just a few centuries back, travelers and explorers setting off on a voyage were faced with a daunting array of obstacles and dangers, encompassing everything from pirates and bandits to weather and disease.

Perhaps most unnerving of all, though, was the vast unknown. Maps included huge swaths of ocean and coastline labeled terra incognita. The edges of charts often featured sea serpents and bizarre animals that appeared capable of swallowing a ship whole, while tales of blood-thirsty cannibals and native peoples with heads in the middle of their chests abounded.