Teeming Cairo, straddling the Nile, is the capital of Egypt and one of the leading cities of the Muslim world. With 20 million people, greater Cairo pulses with energy. We explore the back streets on a tuk-tuk, drop in on a mosque, haggle with a gauntlet of eager merchants, bake some pita bread, marvel at King Tut’s gold, greet the ancient Sphinx, and climb into the center of the greatest pyramid.