For most, life in the underworld is not particularly unpleasent. It is rather like a miserable dream, full of shadows, without sunlight or hope. A joyless place where the dead slowly fade into nothingness.
Geographically, the underworld is surrounded by a series of 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 swear), and The Lethe (river of forgetfulness). Once across the rivers an adamantine gate, guarded by Cerberus, forms the entrance to the kingdom. Deep withen the kingdom is Hades vast palace, 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 is a single ferry run by Rhadamanthus, Minos I, and Aeacus, who pass sentence. The very good go to the Elysian Fields. Others are singled out for special treatment. Sisyphus and Tantalus being prime examples of the later.
Tartarus lies far beneth the disk of the world. Deeper then
Hades kingdom of the
underworld. It is used as the ultimate of
prisons, unpleasent and inaccessable.