it depicts the classical subject related by virgil in his "aeneid" (book 6, line 369) and dante in the "inferno" (book 3, line 78) at the centre of the picture within the christian traditions of the last judgment and the ars moriendi. the larger figure in the boat is charon, who transports the souls of the dead to the gates of hades. the passenger in the boat, too minute to distinguish his expressions, is a human soul deciding between heaven, to his right (the viewer's left), or hell, to his left. the river styx divides the painting down the centre. it is one of the four rivers of the underworld that passes through the deepest part of hell. on the painting's left side is the fountain of paradise, the spring from which the river lethe flows through heaven.