1. Acheron (Acheron): This is the first river Dante encounters as he enters Hell. Acheron represents the sins of the unbaptized and virtuous pagans. To cross it, Dante and Virgil board Charon's boat, which takes them across the river to the second circle of Hell.
2. Styx (Styx): The river Styx is located in the Fifth Circle of Hell, where the wrathful and sullen are punished. The Styx forms a marsh called the Fen of Styx, where souls are submerged in the mud, constantly fighting and tormenting each other. To cross the Styx, Dante and Virgil board the boat of Phlegyas, another boatman of Hell.
3. Phlegethon (Phlegethon): This is the river of boiling blood in the Seventh Circle of Hell, reserved for the violent against others, against themselves, and against God. Here Dante and Virgil walk along a narrow stone path that traverses the river of boiling blood.
4. Cocytus (Cocytus): The frozen lake of Cocytus is located in the Ninth and final Circle of Hell, reserved for treachery. The lake is divided into four rounds representing different types of treachery. To reach the center of the lake and confront Lucifer, Dante and Virgil traverse the ice by riding on the back of the giant Geryon.
Throughout their journey through Inferno, Dante and Virgil encounter various mythological figures associated with these rivers, who aid or hinder their passage. These rivers serve as symbolic obstacles that Dante must overcome to confront moral and ethical issues, ultimately reflecting his journey of self-discovery and spiritual purification.