The Structure of Dante's Inferno            

Dante's inferno is a funnel shaped structure made up of 9 rings.  Each ring corresponds to a separate type of sinner and that is where those people are sent.  On the top is widest of the rings and they progressively get smaller until the 9th ring, where Lucifer resides.  The rings are labeled as follows:

1st Ring: Limbo- This ring contains those who are just but did not know Jesus Christ.  Members include babies who had yet to be baptized and were without sin.  Many poets and philosophers are found here.

2nd Ring: The Lustful- This ring contains those who committed sins of lust.  Many who were adulterous are found here.  There is a constant heavy wind/rain storm in this ring.

3rd Ring: The Gluttonous- This ring contains those who committed gluttonous sins, especially gossip.  IN this ring there is a constant rain.

4th Ring: The Avaricious and Prodigals- This ring is full of those people who are especially greedy.  They roam around, bumping into one another constantly as they struggle to push large rocks.

5th Ring: The Wrathful and Sullen- This ring's inhabitants are in the river Styx.  The wrathful emerge from the river while the sullen are always fully submerged.  The river is dirty.

6th Ring: The Heretics- This ring is full of those people who did not obey and spoke against the religious law.  Dante finds many open tombs with fire coming out of them.

7th Ring: The Violent-
This ring is split into three different sections.
                                        1.) Violent against their neighbors.  These tyrants and murderers are found in a river of boiling blood called Phlegethon.
                                        2.) Violent against themselves.  The souls of these people are leafless trees in an unnatural forest.  Their leaves are plucked                                                   by the Harpies as soon as they sprout.
                                        3.) Violent against God and nature.  Among these blasphemers is Capaneus who was sent there by Zeus for a rebellion.

8th Ring: Fraud-  This ring is split into ten sections called bolge, or ditches.
                                1.) Panders and Seducers are whipped by horned demons.
                                2.) Flatterers are immersed in excrements.
                                3.) Simonists are set heads down into holes in the rock with flames burning on their feet.
                                4.) Diviners, Astrologers and Magicians heads are turned backwards, so they have to walk backwards.
                                5.) Barrators are plunged into boiling pitch and guarded by ten sneaky demons (Malebranche) led by Malacoda (evil tail).
                                6.) Hypocrites, mostly monks of the Jovial order, walk slowly, clothed in heavy caps of lead.
                                7.) Thieves who keep changing into snakes.
                                8.) Fraudulent Counselors who slide away in the ditch as flames.
                                9.) Sowers of Discord and Schism who are physically torn apart.
                               10.) Falsifiers of metals, persons, coins and words are kept in a sort of large hospital with people with all kinds of deformities. As                                       in the previous ditch, this too is crowded.

                         A thief changing into a snake---->
9th Circle: Treachery- This ring is split into four different section, though all of the sinners are submerged in ice.
                                        1.) Caina: Traitors to Kin are immersed in the ice with head down.
                                        2.) Antenora: Traitors of Homeland. Dante sees one who keeps biting on another's head.
                                        3.) Ptolomea: Traitors to Guests are head up in the ice, which is freezing their eyes.
                                        4.) Giudecca: Traitors to Benefactors are completely immersed into the ice.

Source- The Physical Structure of Inferno