As seen at The World of Dante, an illustration by Lindsay McCulloch.
Speaking to Kotaku commenters during today's live chat, Dante's Inferno producer Jonathan Knight said that the real "ah ha" moment for him in deciding whether Dante's Inferno the book could be turned into Dante's Inferno the video game was seeing a map of hell.
"The real "ah ha" moment for me was seeing this really cool map that someone created of the 9 circles of hell. You see a lot of these maps, you know the "V" shaped cross section, but there was one in particular that had all the call-outs for the different sections, the "bosses" of each circle (Charon, Minos, Cerberus, etc.), and I just looked at that map and said, "that's a level-based game waiting to happen."
See the full-sized pic here.