Hell was apparently found inside the earth and comes divided into nine rings and believe it or not-an antechamber! Sort of a pre-hell. There reside those cherubs who took no sides in the Rebellion of Angels (you remember the revolt against God led by Satan). Apparently, there were a fair number of angels who chose to wait out the conflict to see who won; this is never a good strategy in an allegorical war, in fact, it is the one way to get screwed no matter who wins. So these wishy-washy angels hang out just across the river from hell with the souls of humans who did nothing noteworthy in their lives and have neither good nor evil marks on their personal tabula rasa.
Sin it seems is punished metaphorically in or near the Inferno. The punishment is real, assuming you buy the entire cosmology here but the particular slings and arrows are apportioned by infraction and carry their own significance. In the anteroom of hell, for instance, the hesitant angels and ethical couch potatoes are stung my hornets and wasps which serve as metaphors for the sting of their consciences. It's poetry remember.
Following the waiting room of hell, we encounter another well known image, the river Acheron (not the river Styx that's another waterway of the Inferno) and the boatman Charon to carry the damned to hell or in this case the tourist Dante and his dead poet Virgil. Charon puts up a fiery fuss over taking a live human into hell, but Virgil utters some words of wisdom ("This is not the human you are looking for...) and they are allowed to be ferried cross the mersey or some such.
Next, the first actual ring of hell: Limbo.