Mount Olympus is the home to the Olympian Gods. It towers up from the center of the earth. Here, the major gods lived and held court. The gods consumed nectar and ambrosia here. The myths were somewhat vague on whether it was an actual mountain or a region of the heavens. In real life, it is Greece's highest mountain and lies on the border of Macedonia and Thessaly
The underworld was hidden in the earth and was the kingdom of the dead and ruled over by Hades. Hades was said to be greedy god who was greatly concerned with increasing his subjects. Those whose calling increased the number of dead are seen favorably by Hades. The Erinyes were welcomed guests. As someone consumed with greed, he was exceedingly disinclined to allow any of his subjects leave.
Life in the underworld was not particularly unpleasant. It was rather like a miserable dream, full of shadows, without sunlight or hope. It was a joyless place where the dead slowly fade into nothingness.
Geographically, the underworld was surrounded by a series of five rivers: The Acheron (the river of woe), The Cocytus (the river of lamentation), The Phlegethon (the river of fire), The Styx (the river of unbreakable oath by which the gods swear), and The Lethe (the river of forgetfulness). Once across the rivers, an adamantine gate, guarded by Cerberus, formed the entrance to the kingdom. Hades' vast palace was deep within his kingdom, complete with many guests.
Upon death, a soul is lead by Hermes to the entrance of the underworld and the ferry across the Acheron. There was a single ferry run by Charon to take the souls across the river. Only those who can pay the fare, with coins placed on their lips when buried, received passage. Those who could not pay were trapped between two worlds. The souls then entered through the gates. Cerberus would allow all to enter but, none to leave. The souls then appear before a panel of three judges, Rhadamanthus, Minos, and Aeacus, who pass sentence. The very good went to the Elysian Fields. Others were singled out for special treatment.
At once, he was both a place deep beneath even the underworld and a personification of the place. So dark and sunless was Tartarus that its gloom has its own personification - Erebus. To reach Tartarus, an anvil dropped from the surface would fall for nine days. It was below the roots of the earth and the sea. Surrounded by a bronze fence with gates of iron, it was used as the ultimate place of imprisonment. The Hecatoncheires acted as its guards. Zeus imprisoned most of the Titans here.