I have been allowed to look into the hells and see what they were like inside, for when it pleases the Lord, a spirit or angel who is overhead can probe visually into the depths and examine their nature with no coverings in the way. I have also been allowed to explore them in this fashion. Some of the hells looked to me like caves and caverns leading into cliffs and then slanting downward or off at an angle.
Some of these hells looked like the lairs or dens of wild animals in the woods, some like the vaulted chambers and crypts found in mines, with caverns leading downward. Many of the hells are threefold. The higher ones look gloomy inside because the people there are fond of malicious distortions. The lower ones look fiery, though, because their inhabitants are devoted to malice itself. Darkness in fact corresponds to malicious distortions, and fire to the actual malice. That is, the people in the deeper hells are the ones who acted from evil on a deeper level, while the people in the hells that are not so deep acted from evils on a more superficial level—that is, on the basis of their malicious distortions.
In some hells you can see what look like the ruins of houses and cities after a fire, where hellish spirits live and hide out.
In the milder hells you can see crude huts, sometimes grouped in something like a city, with alleyways and streets. There are hellish spirits in these homes, with constant quarrels, hostility, beating, and violence. The streets and alleys are full of thieves and robbers.
In some hells there are nothing but brothels, foul to look at and full of all kinds of filth and excrement.
There are also dark forests where hellish spirits roam like wild beasts; and there are underground caves there where they flee when they are being threatened by others. Then there are desert areas where everything is barren and sandy, with rugged cliffs here and there with caves in them, and huts scattered around as well. People are exiled from the hells into these desert places if they have suffered to the limit, especially people who in the world were craftier than others in the skills of deliberate manipulation and deceit. This kind of life is their final lot.
from Heaven and Hell, Section 586