Final answer:
The third holiest city in Islam after Mecca and Medina is Jerusalem, due to its association with the Prophet Muhammad's ascension to heaven and the presence of the sacred Al-Aqsa Mosque and the Dome of the Rock.
Step-by-step explanation:
The third holiest city in Islam, after Mecca and Medina, is Jerusalem. This significance dates back to the Prophet Muhammad's journey to heaven, which is believed to have started from Jerusalem. The Al-Aqsa Mosque, situated on the Temple Mount, is particularly sacred because it is regarded as the location from which Prophet Muhammad ascended to heaven during the Isra and Mi'raj event. Moreover, Jerusalem is also the site of the Dome of the Rock, important to Islamic tradition as the place where Muhammad began his night journey and associated with prophetic figures in Islam, Christianity, and Judaism.
Thus, Islam's holy cities — Mecca, Medina, and Jerusalem — are central to the faith of Muslims worldwide, with the Kaaba in Mecca being the holiest site where millions of Muslims perform the Hajj pilgrimage annually. Importantly, these cities provide structure, consistency in daily life, and are a unifying force within the Muslim community. While Mecca and Medina are in Saudi Arabia, Jerusalem is a multifaceted city with historical and religious significance to Jews and Christians as well.