It is said that there was civilization before and that there were humans like in Zerrikania and Haakland and that they have unique culture and architecture, but maybe because of desertification left this place (or died of hunger) and their cities were smothered.
Time of Contempt (book) Edit
Because the portal was unstable, the girl was simply ejected in mid-air over the desert. When she finally regained consciousness, Ciri had no idea where she was, nor how to get out of the desert. She had no food nor water with her and her only defenses were one small dagger and her wits. She did meet a young unicorn and together they were better able to proceed than alone.
*To be added