A 15-year-old boy might need to feel advanterous

 

Have him read about those events and then take him to visit the places where they took place, to see the marks they left.

You can start with dark-tourism.com. Pick a place that you think is suitable for him. For example, there was a movie a few years ago, "Anthropoind". Watch it with him, and ask him if he wants to see the church in Prague.

Let him lead you.