Mecca
Islam's most sacred cities of Mecca and Medinah are in the Kingdom of Saudi Arabia.
Hajj is the pilgrimage to Mecca in Saudi Arabia. Hajj means "standing before a deity in a sacred place" or "voyage to a sacred place." Mecca is the most sacred of the Muslim cities.
They don't. That is Islam.
Mecca
If by the Sacred Mosque you mean the Great Mosque in Mecca, yes it is.
Mecca, in Saudi Arabia, is Islam's most sacred city.
There are many sacred cities in the Middle East. Jerusalem is one. Mecca is another.
The sacred object in Mecca is a stone believed to have fallen from heaven. It is not a body part.
Mecca is the Holy Land not the city
Makkah (or Mecca) in the Kingdom of Saudi Arabia
The first Islam State Capital was Medina, then Damascus, then Baghdad. Never Mecca was an Islamic state capital although Mecca is the most sacred Islamic city.