The Greek underworld, in mythology, is an otherworld where souls go after death, and is the original Greek idea of afterlife. At the moment of death the soul is separated from the corpse, taking on the shape of the former person, and is transported to the entrance of the Underworld. The Underworld itself is described as being either at the outer bounds of the ocean or beneath the depths or ends of the earth. It is considered the dark counterpart to the brightness of Mount Olympus, and is the kingdom of the dead that corresponds to the kingdom of the gods. Hades is a realm invisible to the living, made solely for the dead.
There are five main rivers that are visible both in the living world and the underworld. Their names were meant to reflect the emotions associated with death.
The Styx is generally considered to be one of the most prominent and central rivers of the Underworld and is also the most widely known out of all the rivers. It's known as the river of hatred and is named after the goddess Styx. This river circles the underworld seven times.
The Acheron is the river of pain. It's the one that Charon, also known as the Ferryman, rows the dead over according to many mythological accounts, though sometimes it is the river Styx or both.
The Lethe is the river of forgetfulness. It is associated with the goddess Lethe, the goddess of forgetfulness and oblivion. In later accounts a poplar branch dripping with water of the Lethe became the symbol of Hypnos, the god of sleep.
The Phlegethon is the river of fire. According to Plato, this river leads to the depths of Tartarus.
The Cocytus is the river of wailing.
Oceanus is the river that encircles the world, and it marks the east edge of the underworld, as Erebos is west of the mortal world.
Entrance of the Underworld
In front of the entrance to the underworld live Grief, Anxiety, Diseases and Old Age. Fear, Hunger, Death, Agony, and Sleep also live in front of the entrance, together with Guilty Joys. On the opposite threshold is War, the Erinyes, and Eris. Close to the doors are many beasts, including Centaurs, Gorgons, the Lernaean Hydra, the Chimera, and Harpies. In the midst of all this, an Elm can be seen where false dreams cling under every leaf.
The souls that enter the Underworld carry a coin under their tongue to pay Charon to take them across the river. Charon may make exceptions or allowances for those visitors carrying a certain Golden Bough. Otherwise, Charon is appallingly filthy, with eyes like jets of fire, a bush of unkempt beard upon his chin, and a dirty cloak hanging from his shoulders. Although Charon embarks now one group now another, some souls he keeps at distance. These are the unburied where they can't be taken across from bank to bank if he had not received burial.
Across the river, guarding the gates of the Underworld, is Cerberus. There is also an area where the Judges of the Underworld decide where to send the souls of the person — to Elysium, the Fields of Asphodel, or the Fields of Punishment.
While Tartarus is not considered to be directly a part of the underworld, it is described as being as far beneath the underworld as the earth is beneath the sky. It is so dark that the "night is poured around it in three rows like a collar round the neck, while above it grow the roots of the earth and of the unharvested sea." Tartarus is the place that Zeus cast the Titans along with his father Cronus after defeating them. Homer wrote that Cronus then became the king of Tartarus. While Odysseus does not see them himself, he mentions some of the people within the underworld who are experiencing punishment for their sins.
Fields of Punishment
The Fields of Punishment was a place for those who had created havoc on the world and committed crimes specifically against the gods. Hades himself would make the individual's punishment of eternal suffering based on their specific crime.
Fields of Asphodel
The Asphodel Meadows was a place for ordinary or indifferent souls who did not commit any significant crimes, but who also did not achieve any greatness or recognition that would warrant them being admitted to the Elysian Fields. It was where mortals who did not belong anywhere else in the Underworld were sent.
Vale of Mourning
The Vale of Mourning is where those who were consumed by unhappy love dwell.
Elysium was a place for the especially distinguished. It was ruled over by Rhadamanthus, and the souls that dwelled there had an easy afterlife and had no labors. Usually, those who had proximity to the gods were granted admission, rather than those who were especially righteous or had ethical merit. Most accepted to Elysium were demigods or heroes. Heroes such as Cadmus, Peleus, and Achilles also were transported here after their deaths. Normal people who lived righteous and virtuous lives could also gain entrance such as Socrates who proved his worth sufficiently through philosophy.
Isles of the Blessed
The Isles of the Blessed were islands in the realm of Elysium. When a soul achieved Elysium, they had a choice to either stay in Elysium or to be reborn. If a soul was reborn three times and achieved Elysium all three times, then they were sent to the Isles of the Blessed to be sentenced to eternal paradise.