i'd check to see if Jesus actually performed any miracles and get what he actually taught, see the dinosaurs, check to see if aliens did visit the earth, and see all my favorite bands live when i damn well please. if i can't change history, then i'm more or less observing, so i couldn't crowd surf or mosh or anything like that, cause even the slightest bump changes that smallest bit of history, so the concerts won't be as awesome, but i'll still check it out anyway. i'd basically observe all religious moments and see how accurate their beliefs really are.