Strangers in a Strange Land, our tour of Death Valley and the Mojave Desert of eastern California. The first was the salt pan at Badwater, the lowest point in North America at minus 282 feet, and Bonnie Claire Playa, where rocks seem to have a mind of their own.
Playas have to be counted as pretty much the flattest places on Earth (abyssal plains on the deep ocean floor are pretty flat, too, but aren't exactly accessible). And they are flat. When rare flash floods bring clay-rich water onto the playa surface, the water spreads out, and the clay stays in suspension long enough to be spread evenly across the lake.