Virgil informs Dante that they are now approaching Lucifer, once the fairest of angels before he rebelled against God. As they walk along, Dante sees souls whose entire bodies are frozen within the ice he and Virgil walk upon. The two poets come to where Lucifer is and Virgil shows him to Dante. Dante says that he cannot express in words how terrible the sight was and that he felt neither death nor life in this deepest part of hell.
Lucifer's upper body sticks out of the ice and Dante says that Lucifer is even larger than the giants he saw earlier. In fact, Dante is closer to the giant's size than the giants are to Lucifer's. Dante describes Lucifer's head as having three faces joined together. The middle is bright red, while the one on the right is a yellowish color and the one on the left is dark.
Lucifer has wings larger than any ship's sails that Dante has ever seen. The flapping of these wings causes the gusts of wind that Dante felt before. Tears and blood drip down his three faces, while each mouth chews upon a different sinner. In the middle mouth is Judas, who betrayed Jesus. The other two mouths consume Brutus and Cassius, who betrayed Julius Caesar.
At the core of hell, Dante places not only arguably the worst sinner in the biblical tradition (Judas) but also two figures of ancient Roman history, who infamously betrayed not Jesus or God, but the Roman hero and almost-emperor Julius Caesar. Judas is the worst sinner, as he betrayed God. Dante seems to suggest that Brutus and Cassius follow just slightly after because they killed the greatest example of secular power the world has known, Julius Caesar, who ruled Rome (the center of Italy) when the Roman Empire (which Dante revered) was at its height.
Virgil tells Dante that they have now seen all of hell. They wait until an opportune time and then climb up onto Lucifer's monstrous body. Dante holds tight to Virgil as they make the perilous climb up Satan's body. At last, they reach the height of an outcropping of rock where they can rest. Dante looks out from it, expecting to see Lucifer's head, but sees his legs stretching up before him, as if everything is upside down.
The reversal of what Dante expects to see during his short break from climbing up Lucifer emphasizes the bizarre strangeness of his unbelievable, otherworldly journey. Having learned all he was to learn from hell, Dante is now ready to proceed to purgatory.
Virgil tells Dante to get on his feet again, because they must continue their journey, even though the road is difficult. Dante asks why things seem to have turned upside down and Virgil explains that they have passed beyond the center of the earth to the southern hemisphere. After climbing up to Lucifer's head, Virgil had to climb back down the other side of him to go back toward the earth's surface. Virgil tells Dante that the southern hemisphere is entirely ocean now, because when Lucifer fell from heaven, he fell through this part of earth and the land fled from him.
Virgil's geography lesson situates the strange world of hell precisely in relation to the earth. Hell seems entirely different from and other than earth, yet Dante locates it under the earth's surface. The two worlds are thus part of the same planet. For Dante, this life and the next are radically different but also crucially connected.
Dante describes a cavern as far from Lucifer through the earth as Lucifer is from the earth's surface where Dante started (in other words, it is near the earth's surface exactly opposite from where Dante started). Here, a small stream trickles and by following that stream (the beginnings of the river Lethe), Dante says that Virgil led him out of hell. At long last, Dante crawled out of hell through a hole, onto the island where Mt. Purgatory is located. Dante can look up and once again see the bright stars in the sky, which he hasn't seen since entering hell.
Dante's version of the river Lethe from classical mythology guides Virgil and him out of hell. Virgil has completed the first stage of his miraculous journey and now re-enters the earthly world. His exit from the world of suffering and sin is signaled by the bright light of the stars in the sky that he can finally see again: he has emerged again into clarity and the light of God's love.