Empires throughout time and all over the world have had not only a local impact on the imperial city (the seat of power) but also a global impact---on settlement patterns, national borders, cultural identity, and city form. But empires have a lifespan, and as our own (the U.S.) empire faces obvious decline, it is interesting to look at the precedent of past empires to understand how a former world power adjusts to a new identity. How does a city once grandiose in its power and influence come to terms with a new global order? Four cities provide interesting models: