In the eleventh book of Homer's Odyssey, the title character must consult the spirit of the Theban prophet Teiresias to find out what further steps he must take to bring his journey and wanderings to an end.
Obviously, the souls of the dead come from the underworld ("the ghosts of the dead swarmed out of Erebus"; A.S. Kline translation), but where is Odysseus standing when he encounters these souls?
After leaving Circe's island (Aeaea), Homer tells us that Odysseus sails all day long until the sun sets. Then, he comes to the Ocean "that surrounds the earth". At some point after that, Homer does not specify, Odysseus reaches "the city and country of the Cimmerians", who are a people who live in perpetual darkness. Thus, in the land of the Cimmerians, Odysseus and his men disembark and make their way "along the Ocean stream" until they come "to the place Circe described".
Circe's description occurs in Odyssey 10:
…beach your ship by the deep swirling waters on a level shore, where tall poplars, and willows that shed seed, fill the Groves of Persephone. Then go to the moist House of Hades. There is a rock where two roaring rivers join the Acheron, Cocytus, which is a tributary of the Styx, and Pyriphlegethon.
Thus, it appears that Odysseus is near Hades' house and near a rock by two of the rivers of the underworld are located.
the underworld, but he gets too freaked out and he leaves