The term "Hades" in modern terms is now considered to be the ancient Greek equivalent to hell, this though is a misconception, as Hades was in fact the domain of the afterlife, and would include what we now consider to be both heaven and hell.
As you would expect from ancient Greece there is no one definitive description of just what Hades is like, or the geography of it, and although I have tried to provide a logical progression through the domain of Greek god Hades, it is not something that is always possible.
The ancient Greeks recognised that everyone would eventually die and would progress to the Underworld, or Hades. The entrance to Hades though is not a defined place, unlike the Roman equivalent that placed an entrance near to Naples. In Homer's Odyssey, the entrance is placed across the water, beyond the Oceanus River, and through the adamantine gates of the setting sun. The tales of Theseus though also point to there being six land based entrances around the coast of the Saronic Gulf, each entrance guarded by a bandit, Orpheus entered through one of these entrances. Heracles and Dionysus also entered by a different path, the Alcyonian Lake.
Once past the gates everyone would then enter into a cold and misty environment. Newly deceased would then need to cross the rivers of Hades. Most people will have heard of the River Styx, this though is only one of five rivers, and was not even the first river to cross. The first river was the river of sorrow, the Acheron. This is the river that the ferryman, Charon, transfers the dead. Charon would take a fee for his work his two coins that had been placed on the eyes of the deceased, or a single obolus placed under the tongue. Not all people though were buried with the proper fee, and these became the lost souls who would crowd the banks of the Acheron for a hundred years.
Four further rivers were also to be crossed. These were the River Cocytus, the river of lamentation; the River Phlegethon, the river of fire; the River Lethe, or pool, which was the river of forgetfulness; and the most famous River Styx, the river of hate.
Charon though would take people backwards and forwards as long as they could pay the fee, it was therefore necessary to have an additional guard in place to prevent people from escaping from Hades. This guard was Cerberus, a three or more headed dog, assigned with the task of allowing no one to leave.
Entering passed Cerberus though was no problem and the deceased would then enter the Asphodel Fields or Meadows. Here the souls of the heroes and ordinary would mix before moving on to the Plain of Judgement. As with most other cultures, the dead would then have to answer for the actions and deeds they had undertaken during their lives. Judgement was undertaken by a triumvirate of judges; Aeacus, Minos and Rhadamanthus, who came to their decision as they sat in front of the palace of Hades, the god, and his wife Persephone. Aeacus in life had been the king of Aegina, as well as a son of Zeus and Aegina. Minos had been king of Crete and son of Zeus and Europa, and Rhadamanthus was his brother and also a prior king of Crete.
The three judges would come to a decision of what would happen to the soul of the deceased. If the life had been lead where the good and evil had balanced themselves out then the soul was returned to the Asphodel Fields to live out eternity. For those that whose life was said to have been evil, then they were consigned to Tartarus, or hell in modern terms.
Tartarus had long played an important role in Greek mythology. In the time before the Olympian gods, it had acted as a prison. Chronos, the supreme Titan, had imprisoned his offspring, the Cyclopes and the Hecatonchires, in Tartarus, and guarded by the dragon Kampe, so a prophecy of his overthrow could not occur. Zeus, also used it as a prison after he was victorious in the Titanomachy, imprisoning the majority of Titans, who were then guarded by the gigantic Hecatonchires. The Titans were joined by later prisoners, including the monster Typhon, as well as Tantalus and Ixion. Escape from Tartarus was said to impossible, as Tartarus was at a depth of forty thousand miles, as approximated from the assertion that a bronze anvil would fall for nine days before it reached Tartarus.
Just as there was a hell in Hades, there was also a heaven, and this was the Islands of the Blessed, also known as the Elysian Fields. The Elysian Fields were for those judged virtuous by the triumvirate, as well as the dwelling of the heroes. Little is said about the Elysian Fields in the Greek tales, although it would appear that all heroes were judged to be virtuous no matter what their deeds. Some tales though do state that Zeus at some point released his father, Chronos, from Tartarus to rule over paradise.
Hades, the Underworld, plays a major role in a number of other Greek tales. The Greek hero Theseus travelled into Hades with Pirithous in order to abduct Persephone, who Pirithous wished to marry. Hades, the god though realised why the pair had entered into his domain and trapped them in the two Chairs of Forgetfulness. Theseus was only rescued from his chair by the efforts of another hero, Heracles. Heracles had made his way into Hades in order to complete his twelfth task of kidnapping Cerberus.
Orpheus also entered Hades in search of his deceased wife, Euridice. Euridice had died as a result of a snake bite, and Orpheus sought to bring her back to the surface world. Orpheus had acquitted himself well as a member of the crew on the Argo, and used his skill as a musician to get pass both Charon and Cerberus. He was able to plead his case in front of Persephone and Hades, and Persephone gave him his chance to regain his lost love. Orpheus though had to return to the surface without looking back, something that he was unable to do, as he sought to see Euridice before exiting Hades, and so lost her forever.
Few people were allowed to leave Hades once they had entered, although Persephone and Adonis were to spend parts of their lives below and above ground. One of the most famous tales of an escapee though is that of Sisyphus. Sisyphus, a king of Thessaly, had been a sent to Tartarus for his crimes against gods and men, he tricked Persephone though in releasing him for a short time to speak to his wife. He was though supposed to return immediately afterwards, but refused. His escape though was short lived though, as Hermes forced him to return.
There are other famous tales of Greek heroes venturing into Hades, including Odysseys and Aeneas. Both though only travelled to seek advice, and neither entered the furthest reaches of the Underworld.
As previously said the story and geography of Hades, the Underworld, is not an easy one to put down in writing. The account provided here is but a small description of what Hades was, and is only one version of a storyline that can be very complex.