Samarra on the Tigris became the capital of the Abbasid empire in 836 when Caliph Motassim moved the seat of the caliphate to Samarra. Its role was shortlived, the caliphate was returned to Baghdad already in 892. Remains of the Friday Mosque with its spiral minaret. The prayer hall of the mosque was gigantic - 15 aisles. When planning for the minaret Caliph al-Mutawakkil (847-861) took up the Sumerian-Assyrian-Babylonian tradition of the sacred tower. The spiral minaret accordingly is an early Islamic echo of the Tower of Babel. With it the Caliph boldly countered the misunderstanding caused by the Biblical polemic and by a similar allusion to the Babylonian tower in the Koran. The ziggurats were never fists rebelliously shaken against heaven; instead the temple towers were an invitation to God to descend and live among the needy mortals. The circular shape of the Malwiya ("the spiral") stresses the desire for cosmic unity. Iraq.