But when, as they went along the rugged path, they were near the city, and had come to a well-wrought, fair-flowing fountain, from which the townsfolk drew water - this Ithacus had made, and Neritus, and Polyctor, and around was a grove of poplars, that grow by the waters, encircling it on all sides, and down the cold water flowed from the rock above, and on the top was built an altar to the nymphs where all passersby made offerings. Homer, "The Odyssey" 17.205 Trans. A. T. Murray. Cambridge, Mass.: Harvard Univ. Press. 1995
The altar for the gods is built up from stones; for the dead there is a ground-level hearth, eschara, or a pit, bothros, which points into the depths. Burkert, Walter. Greek Religion. Trans. John Raffan. Cambridge, Mass.: Harvard Univ. Press. 1985
The altars which stand in the open air do not have fire burning on them continuously, they are kindled in an impressive ceremony in the course of the festival. Burkert, Walter. Greek Religion. Trans. John Raffan. Cambridge, Mass.: Harvard Univ. Press. 1985
There are natural rock altars; altar and cult stone are then identical. In simple rustic shrines a few stones roughly set together may serve as an altar. In a number of large and important sanctuaries the remains of ash and bone are allowed to grow up into great mounds; even at Olympia this and nothing else was the altar of Zeus. The normal Greek altar, however, is well built, constructed of bricks and white-washed with lime or else fitted together from carefully hewn stone blocks. Not infrequently the sides are decorated with volutes. In between lies the metal tablet on which the fire burns. Burkert, Walter. Greek Religion. Trans. John Raffan. Cambridge, Mass.: Harvard Univ. Press. 1985
Most Hellenic households had at least three altars, the Hestia, the Apollo Patroos, and the Zeus Herkeios. These altars were the focus of worship and, many times, protective in nature. As a visual reminder of our spirituality, as a work place for religious rituals and as a symbol of the foundation or firmness of our beliefs, the altars of today must look like the most structurally solid object within view.
When she learned that the fated day had come, she bathed her fair skin in fresh water, and taking her finery from its chambers of cedar she dressed herself becomingly. And standing in front of the goddess' altar she made her prayer: 'Lady, since I am going now beneath the earth, as my last entreaty I ask you to care for my orphaned children: marry my son to a loving wife and give my daughter a noble husband. And may they not, like their mother, perish untimely but live out their lives in happiness in their ancestral land!" Euripides, "Alcestis" 158 Trans. David Kovacs. Cambridge, Mass.: Harvard Univ. Press. 1994
The origins of political sociality have often been traced to the conception of a "common hearth." The cult of Hestia and the existence of a "common hearth" for the polis are widespread (perhaps universal) phenomena in Greece. The city hearth is related to the existence of an eternal fire, and both offer a symbolic image of the political community as family group. Vernant, Jean-Pierre, Ed. "The Greeks" Trans. Charles Lambert and Teresa Lavender Fagan. Chicago, IL: Univ. of Chicago Press. 1995
The domestic hearth, for example, around which the family gathered to cook and eat, was dedicated to the goddess Hestia, who protected the prosperity and continuity of family life. Vernant, Jean-Pierre, Ed. "The Greeks" Trans. Charles Lambert and Teresa Lavender Fagan. Chicago, IL: Univ. of Chicago Press. 1995
The hearth was the center of the house cult and of the piety of daily life. We should remember that while our piety is expressed chiefly in words, by prayers, the piety of the ancients was expressed chiefly by acts. Nilsson, Martin C. "Greek Folk Religion" Philadelphia, PA: Univ. of Pennsylvania Press. 1940
The first and foremost of these is the Hestia. This is the hearth and center of every household where the family gathers. At every meal, a little of the food and drink are sacrificed at the hearth to make a connection between the family and Hestia, goddess of the hearth.
The next in order of importance is the Zeus Herkeios. This is an altar stone, with a snake engraved on it, which stands at the entrance to the courtyard. Offerings are made here so Zeus Herkeios will protect the courtyard and storerooms.
At the entrance to the home is the Apollo Patroos which is a conical shaped stone which guards the house from outside evils. In later years, the Apollo Patroos was accompanied by an altar to Hekate to protect the house from magical evils and ghosts.
Travelers would frequently come across a pile of stones called a herma. To honor Hermes, you would add another stone to the heap. Sometimes a tall stone, called a herm, was in the middle of the heap as an altar to Hermes. In this case, you would leave something you no longer needed as an offering to Hermes or if you were in real need of something at the altar, you would take it as a gift from Hermes.
Finally there are the public altars, for festivals and public rituals. The altars for sacrifices to the Olympians are made of whitewashed brick or well-fitted stone and raised off the ground. The altars for sacrifices to the chthonic deities are fires on the ground, pits or natural crevasses called megara.