Located in one of the flattest places on the face of this planet are the unexplained Sailing Stones of Racetrack Playa, Death Valley, California. The rocks move leaving clearly visible tracks behind them.
If you want to see Death Valley in a day, then it calls for a very very early start. This depends on where you're from. It was a bit over a 4 hours drive from Los Angeles. I spent two days in Death Valley;