Pandemonium is described as the central heart and capital city of Hell itself.
The demons built it the main building about an hour, but it far surpassed all human palaces or dwellings; it may have been small, however, as its spacious hall is described as being very crowded with the thronging swarm of demons, who were taller than any human man, until at a signal they were shrunk from their titanic size to less than "smallest dwarfs". It was also reputed to be made of solid gold.
Pandemonium is the name for the capital of Hell, the High Capital of demon-kind following under the Seven Princes of Hell. It was built by the fallen angels under the command of Mammon and was designed by the architect Mulciber, who had been the designer of the palaces in Heaven before his fall.
The city also acts as a central hub for the main royal line of demons and fallen angels of Hell. It is where the Stygian Council presides in and is regarded as the seat of power within the Inferno. It is also the abode of Lucifer and one of which he shares with Beelzebub. In addition, Beelzebub is said to hold meetings among the Order of the Fly, his personal court, within Pandemonium alongside several members of the Ars Goetia.
After the fall of the Watchers, or the second fall of the angels, they were said to be punished by God by having Michael chain them within the deepest chasms of the earth. However, it is revealed that some of the Watchers were punished by having to carry the entire capital of Pandemonium onto their shoulders and backs for all eternity.