Pandæmonium (or Pandemonium in some versions of English) is the capital of Hell in John Milton's epic poem Paradise Lost.
Pandæmonium thus roughly translates as "All Demons"—but can also be interpreted as Pandemoneios (Παν-δαιμον-ειον), or 'all-demon-place'.
John Milton invented the name in Paradise Lost (1667), as "A solemn Council forthwith to be held at Pandæmonium, the high Capitol, of Satan and his Peers" [Book I, Lines 754-756], which was built by the fallen angels at the suggestion of Mammon.
Book II 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 was probably quite 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".