East City is a very large urban area, centered around what was, in our times, the Boston-New York-Philadelphia-Washington area, in eastern United States. It looks similar in many ways to the "Sprawl", as described by William Gibson in his novels.
In the XXII century, in which the Nathan Never adventures are set, it's the largest city of the world, and one of the few areas where humans can still live. The only other large city in North America is West City (or West Coast City), centered around today Los Angeles. In between, there lies a great stretch of land where nuclear radiations have made life impossible, called "the Territory".
A notable feature of East City is that it's made of seven levels of buildings, built one over the other. The lowest levels are the most degraded, populated by marginalized people and mutates, while the seventh level, called the Empireus, is where the wealthiest citizens live and work.
Alfa Building, where the Agenzia Alfa has its headquarters, was initially located in the 6th city level.
The fall of Urania
At the end of the bloody War between the Earth and the Orbiting Stations, a part of the abandoned Station of Urania fell down and crashed in the middle of the City. As a result of this dramatic event, 40% of the buildings were swept away, 40% suffered minor damage, and 20% were damaged in an irreversible way and sooner or later will collapse, including Nathan Never’s old apartment, that was demolished (Nathan Never #162) ... The new Alpha Building (because of its protective shields) was the only building left standing in a huge crater in the center of the city.