I`d like to pay a visit to Leonardo di Vinci. Also, I`d like to see who constructed Stonehenge.
And what he said. Visit DaVinci, he's my idol. Go to the Renaissance, get to know what it was like. I'd come home with a full understanding of it, and be the best Ren Faire participant ever. Along the above lines, meet Shakespeare! I'd get a feel for how he meant his shows to be preformed.
I might to solve some mysteries of the past, for example, I'd go back to the beginning of time and prove that religion is obsolete or that it's true that a deity created mankind.