Why is the Dome of the Rock considered the oldest surviving Islamic monument?

The Dome of the Rock, completed in 691 CE, is considered the oldest surviving Islamic monument because it is the earliest major structure from the Islamic period that remains standing today.12

Built by the Umayyad caliph 'Abd al-Malik ibn Marwan, the monument serves as a masterwork of early Islamic architecture. While its construction techniques and octagonal plan were influenced by the Byzantine tradition, the building is uniquely Islamic in its decoration, which excludes human or animal forms in favor of Arabic script and vegetal patterns.12

Historically, the structure is interpreted as a victory monument intended to assert the religious and ideological claims of the new faith over the holy city of Jerusalem. Although it is often associated with the Prophet Muhammad’s ascension to heaven, contemporary inscriptions suggest it was originally built to emphasize the unity of God and to establish Islam's relationship to existing Abrahamic traditions. Its original structural components have been preserved through the centuries, despite various renovations and decorative modifications by successive dynasties.21