Mecca is a city on Earth. Located in the Muslim Bloc state of Arabia, Mecca is considered the holiest site of the Islamic religion, and those humans of the Islamic faith are required to make a pilgrimage to the city at least once in their lives in possible. The city is located in western Arabia about 80 kilometers from the Red Sea.
Mecca, along with much of the Middle East was particularly hard hit during the Third World War. A nuclear device was detonated in the city in the 2050s. (TLE novel: The Sundered)
By the 24th century, a planet known as New Mecca had been colonized. (DS9 episode: "Second Skin")