From the tombs of the Egyptian Pharaohs to the Titanic's shipwreck, people are pretty good at finding lost treasure. It's part of human nature to be curious. But while there are plenty of mythological treasures that will never be found like the lost cities of Atlantis and Aztlán, these 20 cool artifacts are known to exist... and have still evaded us to this day.

Perhaps the coolest entry on this list is the tomb of the First Qin Emperor in China, the Qinshihuang Mausoleum. Unlike most other examples here, however, we know exactly where it is. The issue lies with what people think is inside. While extensive exploration of the surrounding Terracotta Army has occurred, legend has it that the tomb itself is extensively rigged with traps, and flowing rivers of mercury. Until scientists can find a way to map out the interior from the outside, the risk of harm to archaeologists, and the historical site itself is too high. 

Speaking of tombs, the resting place of Alexander the Great, Cleopatra, and Marc Antony remains undiscovered. You would think such figures might demand elaborate tombs, but many researchers believe they lie beneath the modern city of Alexandria, and thus out of reach.