Glass was not only used to make receptacles — it also served as a flooring material. One side of this tile is smooth-surfaced. The other side, however, is covered with little knobs that would have stuck to the coating on which the tile was set. Such tiles were used only in royal residences. The glassmaking industrial complex at Raqqa, recently excavated by a team of British archaeologists, also manufactured translucid glass tiles like this one, particularly for the palaces of the Abbasid caliph Harun al-Rashid, who lived in this city from 796 to 808. The archaeologists advanced the hypothesis that glass may have been exported to other centers in the Empire in the form of such glass blocks, since they were practical for shipping purposes.