Pandemonium
Location

Pandemonium is the Capital of Hell, where Satan and Astaroth reside.
History
Pandemonium was constructed after the thousand-year war between Satan's and Pluto's factions of fallen angels, which Pluto and his Watchers lost. The defeated watchers built Pandemonium, which rose of their backs.
Gallery
The demons of Pandemonium panic as Hellboy tastes his first pancake.

Inspiration
Pandemonium is clearly inspired by Pandæmonium from John Milton's epic poem Paradise Lost, which was constructed by the 1/3 of the fallen angels that followed the Devil against God.