Nerd out during a 2-hour guided tour of the JPL campus, where space telescopes, planetary orbiters and Mars rovers are designed and tested before they are rocketed into the Final Frontier.
Free! Advance reservations required and can be made online. Tours fill up quickly; luckily, they can be booked 5 months in advance.
You must bring a valid government-issued ID with you (non-U.S. citizens must show a passport).
Be sure to wear comfy shoes and bring bottled water.