Anauroch

A huge desert, Anauroch was created by the demise of Netheril. It runs down the middle of Faerûn, splitting it into east and west.

Resources
The Forgotten Realms Campaign Setting, Ed Greenwood, Sean K Reynolds, Skip Williams and Rob Heinsoo; 2001 Wizards of the Coast Anauroch, Ed Greenwood; TSR 1991