The Nilometer, built in 247 Hegira (861 A.D) during the ‎reign o the Abbasid Caliph Mutawakil-ala-Allah, is ‎considered an important Islamic monument in Egypt. It ‎contains significant architectural elements and ‎calligraphic inscriptions. According to the historian Ibn-‎Khallikan, it was Ahmad Ibn Mohammed al-Hasib who ‎built it, and it was completed in the Arab month of ‎Rajab, 247 Hegira, as mentioned earlier. The name of ‎Caliph Mutawakil was inscribed on one of the friezes ‎inside the Nilometer, but it was removed by the ‎architects of Ahmad Ibn Tulun when the Nilometer ‎was renovated in 259 Hegira. It was restored in 485 ‎Hegira, (1092 A.D) by Badr al-Jammali, minister of the ‎Fatimid Caliph Mustansir. The mosque, known as Al-‎Miqyas (the mosque of the Nilometer), was built next ‎to it. Al-Zahir Baybars built a dome over the well of the ‎Nilometer, which was restored later by Sultan Al-‎Ashraf Qaytbay. During the Ottoman period many ‎other renovations were carried out. More recently the ‎Committee for the Preservation of Arab Monuments ‎restored it 1925 following the collapse of the ‎Nilometer’s base. It was then that the pyramidal cover, ‎presently found on top, was added.‎