Mesquite Sand Dunes sprawls 14 miles across the widest part of Death Valley. Of all the dune areas found in the park, it is the one most accessible. An interpretive sign near the dunes explains that the dunes provide precious water and an escape from the extreme temperatures of the desert for many animals. Sparse rainfall does not go to waste as the grains of sand act like a sponge absorbing water in the space between the grains. We dug with our hands into the sand to check out that theory and could feel the moisture and coolness.