Archeology is fascinating. You know, uncovering and studying past civilizations and cultures. The thing is though, that without all the information, all we can do at this point is speculate. Especially when it comes to civilizations that no longer exist! That’s maybe why there are so many unsolved mysteries about our own past and history. From a great ancient city made out of stone, to underwater ruins of lost civilizations, here are the 20 Most Mysterious Monuments That Cannot Be Explained.