The Underworld, also known as Hades, was hidden deep in the earth and was the kingdom of the dead. It
was the location of the afterlife in Greek mythology. It is not to be confused with the god, Hades, its ruler.
Geographically, the Underworld was considered to have been surrounded by five rivers: the Acheron (river of woe), the Cocytus (river of lamentation), the Phlegethon (river of fire), the Styx (river of unbreakable oath by which the gods took vows and hatred), and the Lethe (river of forgetfulness). Past the rivers, a diamond gate, guarded by Cerberus, formed the entrance to the kingdom. Deep within the kingdom, lay Hades' vast palace, full with guests.
Upon death, a soul was led by Hermes near the entrance of the underworld, where the ferry awaited to carry it across the Acheron. There was a single ferry run by Charon, the boatman who took the souls across the river. Only those who could pay the fare with coins placed on their lips when buried, were granted passage; the rest were trapped between two worlds. After the boat ride, the souls entered through the gates;Cerberus allowed everyone to enter, but none to leave. The souls then appeared before a panel of three judges, Rhadamanthus, Minos, and Aeacus, who passed sentence based on their deeds during their previous life. The souls who were good went to the Elysian Fields, while the others were singled out for special treatment; Sisyphus and Tantalus are two examples of souls that were sentenced to be tormented for eternity.
Taenarum is the entrance to The Underworld, where the dead enter. Before the entrance to Hades live Grief and Anxiety, along with Diseases and Old Age. Also Fear, Hunger, Death, Agony, and Sleep, dwell in this place together with Guilty Joys. On an opposite threshold is War, the Erinyes, and Eris. Close to the doors, many other beasts dwell consisting of Centaurs, Gorgons, the Lernaean Hydra, the Chimera, the Harpies, and others. 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, this 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 where each one is sent to either Elysium, the Fields of Asphodel, or the Fields of Punishment.
Tartarus is the deep abyss that is used as a dungeon of torment and suffering for the wicked and as the prison for the Titans. Well-known residents of Tartarus included is Tantalus, Sisyphus, Ixion, the Danaides, and Tityus. It 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.
The 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.
The 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.
Elysium was a place for the especially distinguished. It was ruled over by Rhadamanthus, and the souls that dwell 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 heros. 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.
The 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.
This river flows from Earth into Hades. This is the entrance to Hades, and Charon rides from here to the River Styx. If you were to bathe in this river, you would be cleansed from the sins you have committed on Earth.
Those who drink from this river have eternal sorrow. It borders Tartarus. Those who are put into Tartarus and the River Phlegethon are to drink from this river.
Those who touch the waters of this River are said to experience complete forgetfulness and amnesia. It flows around the cave which Hypnos lives in. Many souls are required to drink from this River, except for those in Elysium. If one is to be reincarnated, they must drink from it before doing so. It borders Elysium.
This river is opposite of the River Styx, and also borders and flows into Tartarus. It is made of flames and blood, despite being a river. This is where all of the wicked souls go after death, who aren't so evil they go to Tartarus.
The River Styx is one of five infernal rivers in Hades. It is the River of Hatred. If one were to bath in it, they would be invincible except in any spot that wa not immersed in the river ( Achilles and the Achilles tendon). The gods swear on it when making promises. Charon escorts dead souls to Hades and assigns them to the area they are to live in for eternity from here.
The river Eridanos was named several times in Greek mythology. The writer Virgil considered it one of the rivers of Hades, but is not often considered among other writers.
The pool of Mnemosyne was sometimes listed as a body of water in Hades. Named after the titaness of memory, it restored all the knowledge forgotten in the Lethe, and in some versions gave its drinker omniscience.
Judges of the Underworld
Minos, Rhadamanthus, and Aeacus are the Judge of the dead and they are all sons of Zeus. They judged the deeds of the deceased and created the laws that governed the underworld. However, none of the laws provided a true justice to the souls of the dead, and the dead did not receive rewards for following them or punishment for wicked actions.
Aeacus was the guardian of the Keys of the Underworld and the judge of the men of Europe. Rhadamanthys was Lord of Elysium and judge of the men of Asia. Minos was the judge of the final vote.