There are a few South American countries with Valle de la luna's (Moon Valley) on their maps. I have to say that the Valle de la luna in Argentina near San Juan is the best.
Everyone in San Pedro takes the bus out to the Chileno version at sunset. Expect to park along side 10 other buses. You then walk up the dunes to a cliff that looks over the valley as the sun sets. We did not like the look of the bus option so we hired mountain bikes and made our own ways there. The trip takes about 1 hour each way pedalling. Take a torch as it gets pretty dark in the desert after sunset. The stars are amazing! The Valley of the moon itself is impressive but nothing compared to the one in Argentina where you are actually grabbing for an oxygen mask...and start making starlogs as you leave hiking boot imprints in the moon dust behind you.