There wasn't anything to see along the way so we did a big drive. We stopped at "The Pebbles" just south of Tennant Creek with the intention of camping there but once we arrived Matt & I weren't too keen on staying. So we had a lunch break there and drove about another 100km south to the Devil's Marbles which had much more appeal. We arrived about 1:30 and got a good spot and after that the campers just kept coming. It was a very popular spot being the nicest place between Tennant Creek and Alice Springs. There must have been between 50-60 campers in the end making it quite full. We just spent the afternoon relaxing and explored the marbles the next day. They evolved from a granite mass which had cracks in it which allowed water in. The water turned the granite to soft clay which then can be washed away with water causing separation and weathering rounds them off.