vast limestone plateau, extending westward for roughly 400 miles (650 km) from Ooldea in South Australia into Western Australia and northward from the Great Australian Bight (a wide bay) for 250 miles (400 km) to the Great Victoria Desert. The plain occupies 100,000 square miles (260,000 square km) of generally flat surface in bedrock; the elevation averages 600 feet (180 m), but in places it rises to 1,000 feet (300 m). Its vegetation chiefly consists of saltbush and blue bush, with some grasses and flowers appearing after rare winter rains (annually averaging 10 inches 【254 mm】 or less). The Nullarbor National Park preserves rare vegetation and fauna. The plain has many limestone caves, including Koonalda Cave, an important archaeological site. The name Nullarbor is derived from the Latin nullus arbor (“no tree”).

Crossed (1841) by the British colonial administrator Edward John Eyre (Eyre, Edward John), the plain is today traversed 100 miles (160 km) inland by the world's longest stretch of straight railroad track (330 miles 【530 km】) and by the Eyre Highway, nearer the coast. There are scattered sheep stations along the margins, supplied by artesian water.