You don't need to be sitting in a classroom to learn something new. Spend some time at House of Terror and find out more about the world around you.
If you like the word "free" as much as most travelers, you'll be happy to know this museum is precisely that. House of Terror is located in Terezvaros. If you want to keep your sightseeing schedule full while you're in the area, also stop by Parliament Building, Szechenyi Chain Bridge and Buda Castle.