The City: New Arcadia - 2nd largest city of California (pop. 3 million), located roughly where Cambria, CA is located in the real world.
Why is such a large city located there? Well the long and short of it is a spaceship crashed in the region in 1947. Government and private industry set up around the ship to exploit its technology, primarily a suite of
fabricators. Even after decades of use and study, the full potential of these machines has yet to be unlocked. In particular, the aliens that built them placed limitations that prevented them from building machines as complex as themselves. However they could be used to build lower tech machinery and even new specialized fabbers that could build even lower tech devices. A industrial megacity formed over the next few decades as a result of this tech.
Of course, nothing good lasts forever. Several of the original fabbers have been damaged by supervillains and a few have been removed from the spaceship and taken to secure government facilities. Since so little of the actual potential of the fabbers has been unlocked, New Arcadia no longer enjoys the dominance it once knew. The tech of the rest of the world has mostly caught up to it. In some ways, it is a West Coast Detroit. Of course, it is far from dead. Millions still live there and the spaceship itself has the world's only known working interdimensional portal.
The UN and the Ideal created a unique NGO to study and explore the multiverse - a civilian scientific organization known as Multiversal Exploratory Institute (MEI) - it still operates out of New Arcadia and is known as the world's premier scientific organization. So far, they have navigated to 137 dimensions since their founding in 1965 and have documented 7 dimensions in detail. It takes them on average 4 years to successfully discover a new dimension and 95% of all new dimensions are 'empty' - having only stars and dead planets, like virtually all of our own universe. They prided themselves on being an independent group that did not cater to the whims of the US military industrial complex but with the disappearance of the Ideal, this may change. The Ideal did provide partial funding and international law prevents MEI from simply mining valuable minerals out empty universes for profit.
