The future is an unknown, but cast your eyes back far enough into the past and it can get pretty murky, too.
Today, we want to know about the historical enigmas that puzzle you the most. Whether you want an answer to some of the long ago architctural questions that we're still wondering over or if it's a slightly closer historical mystery that's plaguing your mind, tell us about it in now the comments. Please include a picture as well.
Image: Diego Delso.