According to the earliest Greek views, a dark abyss, which lay as far below the surface of the earth as the earth is from the heavens. Above Tartarus were the foundations of the earth and sea. It was surrounded by an iron wall with iron gates set up by Poseidon, and by a trebly thick layer of night, and it served as the prison of the dethroned Cronus, and of the conquered Titans who were guarded by the hecatoncheires, the hundred-armed sons of Uranus.
In later times its signification altered, and it came to mean the lower regions as the place of damnation, in which the wicked who had been condemned by the judges of the world below suffered endless torments.
Later poets describe Tartarus as the place in the lower world in which the spirits of wicked men are punished for their crimes, and sometimes they use the name as synonymous with Hades or the lower world in general; and pater Tartarus is used for Pluto.
(ll. 820-868) "But when Zeus had driven the Titans from heaven, huge Earth bare her youngest child Typhoeus of the love of Tartarus, by the aid of golden Aphrodite . Strength was with his hands in all that he did and the feet of the strong god were untiring. From his shoulders grew an hundred heads of a snake, a fearful dragon, with dark, flickering tongues, and from under the brows of his eyes in his marvellous heads flashed fire, and fire burned from his heads as he glared. And there were voices in all his dreadful heads which uttered every kind of sound unspeakable; for at one time they made sounds such that the gods understood, but at another, the noise of a bull bellowing aloud in proud ungovernable fury; and at another, the sound of a lion, relentless of heart; and at anothers, sounds like whelps, wonderful to hear; and again, at another, he would hiss, so that the high mountains re-echoed.
And truly a thing past help would have happened on that day, and he would have come to reign over mortals and immortals, had not the father of men and gods been quick to perceive it. But he thundered hard and mightily: and the earth around resounded terribly and the wide heaven above, and the sea and Oceanus's streams and the nether parts of the earth."
Theogony of Hesiod
"After these, Earth bore him the Cyclopes, to wit, Arges, Steropes, Brontes, of whom each had one eye on his forehead. But them Sky hound and cast into Tartarus, a gloomy place in Hades as far distant from earth as earth is distant from the sky.
And again he begat children by Earth, to wit, the Titans as they are named: Ocean, Coeus, Hyperion, Crius, Japetus, and, youngest of all, Cronus; also daughters, the Titanides as they are called: Tethys, Rhea, Themis, Mnemosyne, Phoebe, Dione, Thia.
But Earth, grieved at the destruction of her children, who had been cast into Tartarus, persuaded the Titans to attack their father and gave Cronus an adamantine sickle. And they, all but Ocean, attacked him, and Cronus cut off his father's genitals and threw them into the sea; and from the drops of the flowing blood were born Furies, to wit, Alecto, Tisiphone, and Megaera. And, having dethroned their father, they brought up their brethren who had been hurled down to Tartarus, and committed the sovereignty to Cronus."
Theogony Of Apollodorus