A "beveled" style of decorative carving emerged from this dynasty, as did a code of literary etiquette called adab. This dynasty oversaw the failure of its irrigation system in the "black land," or Sawab, south of its capital. Three brothers serving this dynasty sketched many hydraulic automata in a Book of Ingenious Devices. This dynasty briefly persecuted heretics at its mihna court. This dynasty's capital had four gates spaced 90 degrees apart around perfectly round w
A "beveled" style of decorative carving emerged from this dynasty, as did a code of literary etiquette called adab. This dynasty oversaw the failure of its irrigation system in the "black land," or Sawab, south of its capital. Three brothers serving this dynasty sketched many hydraulic automata in a Book of Ingenious Devices. This dynasty briefly persecuted heretics at its mihna court. This dynasty's capital had four gates spaced 90 degrees apart around perfectly round walls. The Barmakid family advised this dynasty early on. A book on solving linear equations, the Al-Jabr, was written by al-Khwarizmi under this dynasty among translators of Greek at its House of Wisdom. For 10 points, name this dynasty of Harun al-Rashid, a caliphate centered at Baghdad which overthrew the Umayyads.