A vast expanse of dunes spread to the horizon like ripples on an ocean. Bursts of wind twirled the reddish gold sand into the air. (45.1)
The Hadarac Desert: another new, strange land that Eragon (along with Saphira and Murtagh and, we guess, the unconscious Arya) must travel through. Out there somewhere is the Varden, a cure for Arya, and the next step in Eragon's adventure. It's just a matter of exploring until they find them.