That's because, prior to today, it had not existed. The inhabitants, the buildings, the roads had all simply materialized in a deserted valley in the Appalachians.  It had taken enormous power- virtually all their dying world had to offer- to transverse dimensions so silently, but it was the only way the Doppel (as they called themselves) could get to this world. This had been their way for millenia. Take over a world, enslave the people there, and use the planet until it was nearly wasted- then move on. Despite numbering only a hundred beings, they had never been defeated in battle, for they observed their foes for years before striking. 

Their weapon was simple- they stole the bodies of their foe's greatest warriors. And they did it through the soft spot of all these races- sex. 

any man or woman coming to the town of Doppel would notice one thing, almost immediately- the men and women (or so they appeared to be- the Doppel had no gender) were all uncommonly attractive. and, soon, that poor man or woman would find their match- their perfect sexual fantasy- for the Doppel, though not strictly speaking telepathic, could read desire, and whichever of them was most suited to the task would take the form of their target's greatest desire- even if that desire was unknown to the target. It wouldn't be long before they would give in to their lust- and,  upon total fulfillment (not merely orgasm, but exhaustion)- the Doppel would strike, switching consciousness with their victim. Not only would they then have control of a great warrior, but the warrior would find themselves in a body far more suited to making love than war.

On this planet, the warriors were called superheroes and supervillains. They had observed them- they had felt the lusts in their hearts- and they had selected targets. Now- to lure them to ecstasy- and doom.