City: Vatican City
The Vatican, with its unparalleled ability to influence more than a billion people, certainly wields enough power to manipulate humanity in a Dan-Brown-esque scheme for the ages. With all the piety and devotion to good that seems to amass on its grounds every day, what's a little satanic ritual or two? New World Order masterminds colluding within such a holy location would only make sense. Deception, after all, is their trade.