Bonus: Cape Canaveral, FL

It’s not cheap, but the John F. Kennedy Space Center—NASA's launch headquarters—has seen some of mankind’s most remarkable achievements. While some details might be lost on kids, they’ll find the daily astronaut-hosted lunches and full-size replica of the Explorer space shuttle truly out of this world. Time it right, and you might get to watch a live rocket launch ($40 for kids 3–11, $50 for 12+).