Between 859 and 861, al-Mutawakkil relocated the Abbasid caliphate temporarily from Samarra to a new settlement that he named Ja'fariya, a site just up the river to the north. The Mosque of Abu Dulaf became the new main congregational mosque not unlike the Great Mosque in Samarra.
The walls of the mosque barely remain, just remnants of the northern façade. Similar to the Great Mosque, the Mosque of Abu Dulaf is enclosed by two ziyadas, the outer one measuring 350 x 362 meters and the lesser enclosure 213 x 135 meters. Its minaret also recalls that of the Great Mosque as it is positioned to the north of the mosque and includes a spiral ramp rising from a square base adorned with small recesses on each side. Later excavations show that the minaret was surrounded by a court with blind arcades like the ones on the socle. This court featured two cisterns.
Forty semicircular towers support the outer wall of the mosque, including four at the corners. Rectangular in plan and measuring 213 x 135 meters, the longest two sides each display six entrance gates whereas the northern façade possesses only three. The interior is organized by sixteen arcades of baked brick including five arches in the sanctuary and three in the northern riwaq, each running north to south with the center aisle being slightly wider than the others. Pioneered here for the first time, these rows form T-shaped piers that buttress another arcade of seventeen arches running east to west . Another freestanding transverse arcade stretches between it and the southern wall. The aisle created from these two arcades intersects the wider central aisle of the sanctuary directly in front of the mihrab forming a T-shaped plan. The Mosque of Abu Dulaf is recognized as a T-plan mosque for this reason. The arcades also end in T-shaped piers at the northern and southern faces of the sahn. Side riwaqs of the mosque are composed of two rows of arcades with nineteen arches exposed to the sahn at each side. Introduced here are piers that are rectangular in shape whereas the ones in the sanctuary and to the north are square-shaped.
Excavation work executed in the 1940s by the Iraqi Department of Antiquities, provides evidence of a double riwaq that extended from the main walls of the mosque off the northern façade and parts of the eastern and western ones, for increasing crowds at Friday prayer. It was also discovered that the mosque was connected to the governor's palace (dar al-imara) by a door just beside the mihrab. It was constructed exclusively of baked brick.
Creswell, K. A. C.1989. A Short Account of Early Muslim Architecture. Rev. ed. Allan, James W. Aldershot: Scolar Press, 367-373.
Ettinghausen, Richard and Grabar, Oleg. 1987. The Art and Architecture of Islam 650-1250. New Haven and London: Yale University Press, 88-92.