coming from pottery kilns and glass furnaces. This smoke may have affected Raqqa/Kallinikos and influenced its decline. It appears that al-Muqaddasi viewed this district as its own distinct city (i.e. madina or misr), which according to legal norms at the time meant that it had to have a separate congregational mosque, and it had to be separated from other urban precincts by some sort of clearly-defined boundary. The congregational mosque may have been the "mosque suspended on columns", or perhaps the Samarran complex near the Bab al-Sibal. Eventually a wall was built on the north side of al-Muhtariqa, probably to protect the central commercial district from Bedouin raids. This is probably the wall that Tahir ibn al-Husayn built while he was governor, in the year following 1 October 815 according to the accounts of Michael the Syrian and Bar Hebraeus. The wall, as visible in old aerial photographs, did not cover the industrial sites north of Raqqa/Kallinikos, leaving them unprotected. Stefan Heidemann suggested that this may have been because those areas were exclusively used for industry, with no houses and no valuables to loot. Five main streets have been identified in al-Muhtariqa. The northernmost runs eastward from the east gate of al-Rafiqah, called the Bāb al-Sibāl, past the still-unlocated northwestern corner of Raqqa/Kallinikos, and then along the north side of Raqqa/Kallinikos before finally ending around Tall Aswad in the northeast. It passes by several mounds of medieval industrial debris in this area exist. These include Tall Fukhkhār, a ceramic producing site; as well as Tall Ballūr, Tall Abī 'Alī, and Tall Zujāj, which were all glass workshops. Henderson and McLoughlin suggested Tall Ballur may have later been a production site again during the late 11th century after 150 years of abandonment, and Tonghini and Henderson suggested the same for Tall Fukhkhar, although Heidemann considered the latter improbable. At the eastern end of this northern street, and to the northeast of Raqqa/Kallinikos, was Tall Aswad. This was the largest and easternmost center of pottery production, and probably the oldest among the industrial mounds excavated. It is a large mound consisting of ruins of kilns, potsherds, wasters, and industrial debris. The site had many kilns producing pottery of various types including unglazed, moulded, and high-quality glazed. It lay at the eastern end of the northernmost main road. Its location was probably chosen because it was downwind from the rest of the city,