The Ascent from Hell and Arrival at Purgatory

Dante and Virgil climb down Lucifer's body, passing through the center of the earth. When they reach the point where the thigh revolves, Virgil turns around and they begin to ascend. They emerge through a natural dungeon into the southern hemisphere, where they see the stars. They are now at the base of Mount Purgatory. Virgil explains the geography: they have passed the center of gravity and are now in the opposite hemisphere. The time is just before dawn on Holy Saturday. This moment marks the transition from the realm of eternal damnation to the realm of purgation and hope.