It's Al- ka'ba.
The Muslims do not worship at Mecca because something happened there. They worship at Mecca because the Black Stone or Kaaba is there. According to Muslims, Abraham used a black asteroid to create a place of worship for God and since the black asteroid is literally a stone from the heavens, it is seen as a closer connection to God.
The Ka'aba
The holy Kaba
Muslims never pray to the black stone at Mecca or to any being in the universe. They pray to only Allah (God in English) as the one and only one God with no son, no partner, no companion, and no associate. The black stone is only kissed by Muslims; if they can reach it; following the practice of prophet Muhammad (PBUH).
Muslims do not worship any city. However, you may be asking which cities are holy for Muslims. The three most holy cities in Islam are Mecca, Medina, and Jerusalem.
Islamic people (Muslims) travel to Mecca on pilgrimages
Mecca is a city in Saudi Arabi. It is the holiest city for Muslims -- when Muslims pray, they allign themselves so that they bow towards Mecca. Mecca is neither in Jeruselum nor in Jordan.
food
The city special to Muslims is Mecca.
Mecca and Jerusalem are holy cities for Muslims.
Ever since Mohammed successfully besieged and conquered Mecca, Muslims have not needed to fight anyone in order to get to Mecca. However, prior to this, the Muslims fought the Qoreish Tribe and other Meccan Tribes in the 620s C.E. for the right to pray in Mecca.
While Muslims are in Makkah (Mecca) they face the Kaaba; the oldest God house on earth.