Can't afford Europe? Take a trip to Georgia and see a henge, well, guidestones. While you're driving around the southeast, don't miss the giant peanut in Plains. That's only one of the many giant peanuts -- and pecans -- to see on your trip.
You could also go to the Coral Castle in Florida. You can prepare yourself by touring the local underground gardens.
Bonus: Lots of strange stuff to think about while you're road tripping: unsolved ciphers, and even some solved ones like the San Jose semaphores that were on top of the Adobe building.
Finally, a big vacation requires big things. This might be the place. They have the perfect hat in case you stop in Iowa on the way back.