Milton visited Rome on his youthful travels and must have seen this monumental masterpiece of baroque architecture, which suggests the kind of effect Milton wanted to evoke by his description of Pandemonium in Paradise Lost, Book I, for (like his father) he saw the unreformed Catholic Church as a diabolic power. Compare the picture above with Milton's description of Pandemonium:

Anon out of the earth a Frabrick huge
Rose like an Exhalation, with the sound
Of Dulcet Symphonies and voices sweet,
Built like a Temple, where Pilasters round
Were set, and Doric pillars overlaid
With Golden Architrave; nor did there want
Cornice or Freeze, with bossy Sculptures grav'n,
The Roof was fretted Gold. Not Babilon
Nor great Alcairo such magnificence
Equal'd in all thir glories, to inshrine
Belus or Serapis thir Gods, or seat
Thir Kings, when Aegypt with Assyria strove
In wealth and luxurie. Th'ascending pile
Stood fixt her stately highth, and strait the dores
Op'ning thir brazen foulds discover wide
Within, her ample spaces, o're the smooth
And level pavement: from the arched roof
Pendant by suttle Magic many a row
Of Starry Lamps and blazing Cressets fed
With Naptha and Alphaltus yeilded light
As from a sky.
(I.710-30)