26. Atlantis
The lost city of Atlantis continues to be a prize among the archaeological community, with many so-called discoveries of the city being debunked. Whether it be off the coast of Greece or in the waters surrounding Japan, there are many theories regarding the existence of the city and its location. While most historians believe it sunk off the coast of Greece, nothing concrete has been discovered; although, some artifacts have been found that could be tied to Atlantis. Maybe one day someone will solve the mystery.