<P> The Dome of the Rock is now mostly assumed to have been built by the order of Umayyad Caliph Abd al - Malik and his son and successor Al - Walid I . According to Sibt ibn al - Jawzi, construction started in 687 . Construction cost was reportedly seven times the yearly tax income of Egypt . </P> <P> A dedicatory inscription in Kufic script is preserved inside the dome . The date is recorded as AH 72 (691 / 2 CE), the year historians believe the construction of the original Dome was completed . In this inscription, the name of al - Malik was deleted and replaced by the name of Abbasid caliph Al - Ma'mun . This alteration of the original inscription was first noted by Melchior de Vogüé in 1864 . Some scholars have suggested that the dome was added to an existing building, built either by Muawiyah I (r . 661--680), or indeed a Byzantine building dating to before the Muslim conquest, built under Heraclius (r . 610--641). </P> <P> Its architecture and mosaics were patterned after nearby Byzantine churches and palaces . The two engineers in charge of the project were Raja ibn Haywah, a Muslim theologian from Beit She'an and Yazid Ibn Salam, a non-Arab who was Muslim and a native of Jerusalem . </P> <P> Shelomo Dov Goitein of the Hebrew University has argued that the Dome of the Rock was intended to compete with the many fine buildings of worship of other religions: "The very form of a rotunda, given to the Qubbat as - Sakhra, although it was foreign to Islam, was destined to rival the many Christian domes ." K.A.C. Creswell in his book The Origin of the Plan of the Dome of the Rock notes that those who built the shrine used the measurements of the Church of the Holy Sepulchre . The diameter of the dome of the shrine is 20.20 m (66.3 ft) and its height 20.48 m (67.2 ft), while the diameter of the dome of the Church of the Holy Sepulchre is 20.90 m (68.6 ft) and its height 21.05 m (69.1 ft). </P>

What is inside the dome of the rock why is it so important