There are some historical mysteries that may never be solved, such as the date of Jesus Christ's birth, the identity of Jack the Ripper, and the location of Cleopatra's tomb.

Sometimes, this is because the relevant material has been lost or because an archaeological site has been destroyed. Other times, however, new evidence is unlikely to emerge, or because what has survived is too vague to convince investigators.

However, the lack of answers makes these riddles all the more interesting.