What are the two other holiest cities in Islam other than the city that  is known for the Hajj?
Hajj: The Hajj ( ; Arabic: ‎ ‎ "Ḥaǧǧ " "pilgrimage") is an annual Islamic pilgrimage to Mecca, the most holy city for Muslims, and a mandatory religious duty for Muslims that must be carried out at least once in their lifetime by all adult Muslims who are physically and financially capable of undertaking the journey, and can support their family during their absence. Holiest sites in Islam:  Mecca, Medina and Al Quds are the three holiest cities in Islam, unanimous among all sects.
Medina and Al Quds