Travel. There is nothing like seeing firsthand how history played out. For example, I was a big fan of Roman and Greek history in junior high school, especially while studying Latin. It all seemed so abstract until later in life when I visited places like Carthage, Sparta, or Rome. Rome in particular, since you can see the progression from ancient Rome with their many Gods, to the times where Christians were persecuted, to the Vatican being the center of the Catholic world, right at the heart of the former Roman Empire. There's something so amazing about that that you can't get from history books or Wikipedia.