CRAU, a region of southern France, in the department of Bouches-du-Rhone, lying east of the eastern arm of the Rhone between the chain of the Alpines and the Mediterranean, west and north-west of the Etang de Berre. It is a low-lying plain, about 8o sq.m. in area, practically desert. Its surface is formed of pebbles (whence the name, from a Celtic root meaning "stone") of all sizes : these, mixed with a proportion of fine soil, overlie a subsoil of stones cemented into a hard mass by deposits of cal careous mud, beneath which lie loose stones, once the sea-bed. Naturally sterile, the Crau is adapted for agriculture by the process of warping, carried out by means of the Canal de Craponne, which dates from the i6th century ; about one-quarter of the region in the north and east has thus been covered by the rich deposits of the waters of the Durance, to which the Crau is said to owe its natural surface. Land which before supplied only rough pasture for sheep, has thus been made to grow the vine and olive ; where irrigation is practicable, water-meadows have been formed. In the uncultivated parts the mirage is said to occur.