The massive Kelso Dunes are easily accessible by car (no four-wheel-drive needed). Second highest sand dunes in California, up to 700 feet. They are created from wind that carries dust and is reflected off a mountain. Beyond their large size, these dunes also have a phenomena called "singing" or "booming" dunes. When the moisture content is right in the sands, they emit a low thrumming sound as sand slides down the slope. Try running down the slope of a dune to trigger the sound. From the parking area, the dunes do not appear to be very far away or very large. This is an optical illusion. Allow at least an hour to climb to the top of the nearest dune.