This indoor zone is the home to the Anaz Mal gnolls. The entrance is a shattered aquaduct at -368.84, -141.48, -1041.48 in the Sinking Sands.
Once inside, it should be noted that in order to reach some aquaducts, you need to climb walls, which are slippery. Right-Click on the wall to obtain the quest to make it able to climb. This quest is called "Slippery Situation".