"Great mosque, Samarra, [was] built...in the caliphate of al-Mutawakkil...This is the largest mosque in the world. Built entirely of brick within a wall flanked with towers, it has a 55 m. high minaret with a spiral ramp that recalls the ziggurats of Mesopotamia."

— Henri Stierlin. Comprende l'Architecture universelle 2. p347.

"The reign of al-Mutawakkil (847 (232 H) - 861 (247 H)) had a great effect on the appearance of the city, for he seems to have been a lover of architecture.Ê In a list of his building projects which appears in several different versions, the new Congregational Mosque and up to 20 palaces are mentioned, totalling between 258 and 294 million dirhams.Ê The new Congregational Mosque, with its spiral minaret, built between 849 (235 H) and 851 (235 H), formed part of an extension of the city to the east, extending into the old hunting park."

— Dr Alastair Northedge and Derek Kennet, The Samarra' Archaeological Survey.