Lake Torrens is usually a dry salt flat. It has only been filled with water once in the past 150 years. It lies 345 km north of Adelaide. Discovered by Edward John Eyre in 1839, for the following twenty years it was believed that Lake Torrens was an enormous horseshoe-shaped saltpan encircling the northern Flinders Ranges and blocking any path to the interior. The first European to penetrate the mythical barrier was A. C. Gregory from the north in March 1858; later the same year, an expedition under B. H. Babbage and Major Warburton in the north-west also crossed the non-existent barrier near modern Marree. Eyre's horseshoe lake was actually composed of Lake Frome, Lake Callabonna, Lake Blanche, Lake Gregory, Lake Eyre South, and Lake Torrens itself.