In the new Discovery Channel documentary, Koppel travels to the border of Iran's border with Iraq, the ancient capital of Isfahan, the holy city of Qom and the Persian Gulf.

NPR: Koppel: Inside Iran, 'The Most Dangerous Nation'

At issue is the Palestinians' claim on east Jerusalem as the capital of the future Palestinian state and the Israelis' insistence that the ancient city remain undivided and in Israeli hands forever.

CNN: Clinton

Start off high and cool in the city of Cuzco (UNESCO World Heritage Site), former capital of the ancient Inca Empire and today the undisputed archaeological king of the Americas.

FORBES: Higher Than A Kite In Peru

Petra is an ancient city that was sculpted out of sandstone cliffs in the southern deserts of Jordan to become the capital of the Nabataeans.

BBC: Experiences that make time stand still

And the Moorish Ummayad dynasty in Spain, made the city of Cordoba its capital, and installed an immense mosque on the site of an ancient Christian church there.

CENTERFORSECURITYPOLICY: A shrine to Shariah?