When John Milton describes hell in book 1 of Paradise Lost, he seems to be portraying a terrifying yet paradoxical place.
At first, he tells us hell is a world where torment and affliction know no limits. He tells of us "bottomless perdition":
Regions of sorrow, doleful shades, where peace
And rest can never dwell.
Hell is not a place to relax, take or break, or unwind. It's a place of constant cruelty and "torture without end." It's so nefarious that Milton can't quantify it.
Yet Milton does quantify it by assigning it concrete properties. He refers to hell as a "dungeon horrible" and a "prison ordained / In utter darkness." Dungeons and prisons have specific boundaries. Yet maybe what separates the dungeon/prison of hell from an ordinary dungeon/prison is that the dungeon/prison of hell offers unlimited capacity.
As for light, there's not lots of that in Milton's hell. As we already know, hell is consumed by "utter darkness." Although, perhaps when Milton says "darkness," he doesn't mean literal darkness. Perhaps he means there's a lack of thought, awareness, or virtue. If it were truly dark, there wouldn't be fires. In Milton's hell, there's "floods and whirlwinds of tempestuous fire."
There's also people in Milton's hell. Maybe not people so much as creatures. There's the fallen angels, including Satan. Satan seems to think of hell as a kingdom—his kingdom. "Better to reign in Hell, then serve in Heav'n," Satan tells the other devils. It reveals the extent to which Satan privileges power. He'd rather rule a place of "waste and wilde" than serve God in a place as perfect as heaven.
One more description that we always take note of occurs when Satan says,
The mind is its own place, and in it self Can make a Heav'n of Hell, a Hell of Heav'n.
The emphasis on the psychological aspects of hell suggests that hell doesn't need specific physical properties or traits. It can exist abstractly in our heads on its own.