As unlikely as it sounds, the Void is just a title that marks the homeworld of the Heartless. It actually is a large city that is devoid of Light forms of life. It is inhabited by no one but the heartless, be it human or creature. Really the city has everything you would find, hotels, stores, plenty of buildings, just no people to really run any of them. The base of operations is located at the top of the highest building in the center of the city.

[Please let me know if this is not an idea you like, I will make changes as needed.]