playa

A dry lake bed in an arid basin — a flat, barren, often cracked surface of fine clay and evaporite minerals marking the floor of a lake that no longer exists, or that exists only briefly after rare rains. Playas are among the flattest natural surfaces on earth. The Bonneville Salt Flats, the Black Rock Desert, and Rogers Dry Lake (where the Space Shuttle landed) are all playas. After rain, a playa can become a shallow, perfectly still mirror reflecting the sky — and then it dries and cracks again.