The citadel, now housing museums, is in the NE corner of the old town. At the north and east side its walls are also the city walls. But to its south and west side there is a specific wall inside the outer walls as such, isolating the citadel. I walked it several times. There used to be populated regions on both sides, but they have disappeared, probably as between 8 November 2015 and 15 May 2016 large parts of Sur were destroyed in fighting between the Turkish military and the PKK. Though I did read a text that indicated at least some of the clearing was voluntary from occupants who were compensated.
To my surprise there turned out to be several small swimming pools in an area I thought was just baking in the heat. It was full of houses on both sides of the wall.