There was at least a small city close to the Ashen Barrens but as the temperature around Desolate Plains of Gahana was too high, almost no humans lived close to it. So the closest place where Sophia was able to land her private jet was in a city called Owtiason. It was actually about 150 kilometers away from the Desolate Plains.
So after landing her plane in the small airport of the city, Rein, Ruby and Sophia started to search for a way to go to the Plains. But as the engines of most vehicles did not work properly because of the high heat, regular vehicles were unable to bring them there.
There were special vehicles called "Danger Rover" which had very high specs and they were able to easily travel even in dangerous locations. Sophia did have one of these but as the plane she had used to land in this small airport was also on the smaller size, she was not able to bring that rover here.