Abū Dulaf, the congregational mosque (masjid jāmiʿ) at al-Mutawakkiliyya in Sāmarrāʾ, Iraq, built during the ʿAbbāsid era. Jaʿfar al-Mutawakkil, the tenth ʿAbbāsid caliph, decided in 245/859 to build a new settlement in the north of Sāmarrāʾ. He lengthened the main thoroughfare of Sāmarrāʾ by three farsangs (approximately 18 km) and dug a canal from the stream …