Pandemonium is described as the central heart of Hell itself. It is the name for the capital of Hell, "the High Capital, of Satan and his Peers", built by the fallen angels at the suggestion of Mammon himself.
It was designed by the architect Mulciber, who had been the designer of palaces in Heaven before his fall. In the epic poem of Paradise Lost, it begins with the debate among the "Stygian Council" in the council-chamber of Pandæmonium.
The demons built it in about an hour, but it far surpassed all human palaces or dwellings; it may have been small, however, as the demons are described as shrinking from their titanic size in order to fit in.