National Air and Space Museum, Washington, D.C.
What's better than one free museum? One that's next to nine other free museums on the National Mall, which offer everything from art to zebras. At the National Air and Space Museum, you'll get an overview of space exploration. Start at the welcome center, where you can pick up a free tour led by museum guides [source: Mullen]. Write down your questions -- the time to have a knowledgeable guide at your mercy is now.
If you'd rather explore by yourself, we suggest getting the back-story on the universe and starting with history -- thousands of years of it. At the "Explore the Universe" permanent exhibit, you'll see the history of astronomy in gadgets, starting with ancient astrolabes and finishing with an engineering model of the Wilkinson Microwave Anisotropy Probe we were just talking about. You can learn the saga of human spaceflight, both the technology and the politics. Roll through a gallery of lunar rover parts and finish with some freeze-dried space ice cream. If you're still not convinced that the stop is worthwhile, you can touch a real moon rock, and who wouldn't want to do that?
Next, it's back to Greenbelt to pick up the car. Then, drive to Virginia to find out where the first astronauts on the moon cleaned up after their lunar adventures before anyone let them walk around on Earth.