I was actually thinking about the particular architecture of the Inferno for a while . Naturally , the graduated nature of each of the cantica is evident , though I would say that the most architecturally detailed is the Inferno . Though that’s not to say that the other two are any less rich , but rather they take on a different kind of richness . It is the difference between the detail of a wrought iron fence and the richness of cheese cake melting in one’s mouth . In a very literal sense , I believe it’s the difference between that which is mundane and physical and that which is ascendant and ethereal . Therefore , it is necessary for the most carnal of the three canticas to have such architectural details as bridges and city walls while the intermediate Purgatorio has natural settings (such as the garden) , and the spheres of heaven are light and aether .