two main passions were "women and building" (""), and accordingly he engaged in major building activities in the capital: he restored and expanded the Great Mosque of al-Mansur which had fallen into disuse; enlarged the Hasani Palace; built the new palaces of Thurayya ('Pleiades') and Firdus ('Paradise'); and began work on the Taj ('Crown') Palace, which was completed under al-Muktafi. This marked the creation of a sprawling new caliphal palace complex, the Dar al-Khilafa, which would remain the residence of the Abbasid caliphs until 1258. Al-Mu'tadid also took care to restore the city's irrigation network by clearing the silted-up Dujayl Canal, paying for this with money from those landowners who stood to profit from it. Theological doctrines and promotion of science In terms of doctrine, al-Mu'tadid sided firmly with Sunni traditionalist orthodoxy from the outset of his reign, forbidding theological works and abolishing the fiscal department responsible for property in escheat, which Hanbali legal opinion regarded as illegal. At the same time he also tried to maintain good relations with the Alids, to the point of seriously considering ordering the official cursing of Mu'awiya, the founder of the Umayyad Caliphate and main opponent of Ali; he was dissuaded only at the last moment by his advisers, who feared any unforeseen consequences such an act might have. Al-Mu'tadid also maintained good relations with the breakaway Zaydi imams of Tabaristan, but his pro-Alid stance failed to prevent the establishment of a second Zaydi state in Yemen in 901. Al-Mu'tadid also actively promoted the traditions of learning and science that had flourished under his early 9th-century predecessors al-Ma'mun (), al-Mu'tasim, and al-Wathiq (). Court patronage for scientific endeavours had declined under al-Mutawakkil, whose reign had marked a return to Sunni orthodoxy and an aversion to scientific inquiry, while his successors had lacked the luxury to engage in intellectual pursuits. Himself "keenly interested in natural sciences" and able to speak Greek, al-Mu'tadid promoted the career of one of the great translators of Greek texts and mathematicians of the era, Thabit ibn Qurra, and of the grammarians Ibn Durayd and al-Zajjaj, the latter of whom became tutor of the Caliph's children. Other notable figures associated with, and supported by, the Abbasid court at the time were the religious scholar Ibn Abi al-Dunya, who served as the Caliph's advisor and was appointed as tutor for al-Muktafi; the translator Ishaq ibn Hunayn; the physician Abu Bakr al-Razi