5/5 - Excellent
Not for the faint hearted as terrain spreads for miles and you certainly don't want to have heart trouble marching over the dunes which also includes a good sense of direction because it would be easy to become disorientated. Have plenty of water to drink, especially when very hot. It is easy to see why the Military use the dunes for training just when you thought you had reached the last there was another vast area with further and even higher sandy hills to climb. Take a bearing using your surroundings.