The prophet Mohammed was born in Mecca, located approximated 50 miles from the Red Sea port city of Jidda, in the year 571 CE. Mohammed fled to Medina, now also a holy city, in the year 622 (ten years prior to his death).
Muslims face Mecca during their daily prayers and one of the key tenets of Islam is a pilgrimage to Mecca at least once in a Muslim's life (known as Hajj). Approximately two million Muslims arrive in Mecca during the last month of the Islamic calendar for the Hajj. This influx of visitors requires a great deal of logistical planning by the Saudi government. Hotels and other services in the city are stretched to the limit during the pilgrimage.
The most holy site within this holy city is the Great Mosque. Within the Great Mosque sits the Black Stone, a large black monolith that is central to worship during the Hajj. In the Mecca area are several additional sites where Muslims worship.
Saudi Arabia is closed to tourists and Mecca itself is off limits to all non-Muslims. Road blocks are stationed along roads leading to the city. The most celebrated incident of a non-Muslim visiting Mecca was the visit by the British explorer Sir Richard Francis Burton (who translated the 100 stories of the Arabian Knights and discovered the Kama Sutra) in 1853. Burton disguised himself as an Afghani Muslim to visit and write Personal Narrative of a Pilgrimage to Al Madinah and Mecca.
Mecca sits in a valley surrounded by low hills; its population is approximately 1.3 million. Although Mecca is definitely the religious capital of Saudi Arabia, remember that the Saudi political capital is Riyadh.