MECCA, Saudi Arabia — As a child, Osama al-Bar would walk from his home past Islam’s holiest site, the Kaaba, to the market of spice and fabric merchants where his father owned a store. At that time, Mecca was so small, pilgrims could sit at the cube-shaped Kaaba and look out at the serene desert mountains where the Prophet Muhammad once walked. Now the market and the homes are gone.