Edited and translated by Lesley Madytinou & Rathamanthys Madytinos
The primary physical feature of Hellenic worship is the altar without which worship becomes difficult . The altar is the foundation of becoming aware of the Gods and the specific place of giving honour to the Divine by mankind. It is not necessarily identical with the sacred, which may be a tree, a fountain or the place itself, but the act of honouring the sacred takes place at the altar. The altar is in fact a man-made gateway to communicate with the Gods and due to this it is imbued with a sacred character .
Even though the altar is the result of human action, after its dedication, it no longer belongs exclusively to the world of humans but acts as a bridge that connects this world with the world of the Gods. Metaphorically we may say that it is a bridge from our world to Olympus or from the human dimension to the divine.
Often we hear it mentioned that the altar is established by the Gods themselves, a hero , or a prominent person. The establishment of an altar by the Gods serves to illustrate the role that epiphany plays in locating and establishing a sacred place while the establishment by heroes or prominent persons requires inherent capabilities of particular people to recognize a sacred place. Regardless of how the altar is established, after its dedication, it cannot be moved . Upon dedication it becomes the foundation for the bridge between the worlds of Gods and men and if moved that bridge will be lost. Archaeology offers many examples of temples or other sacred buildings that have been relocated but the altar always remains in the same place in which it was originally established .
Altars may be categorised into three major categories according to types of worship: residential , sanctuaries, and community . Depending on the type of offerings the altars are also categorised as sacrificial, fiery, non-fiery or bloodless. Depending on the level they are divided into Chthonic, Olympian or altars of the Dead . Each of these categories has significant differences in both their exterior and esoteric characteristics .
Usually altars are dedicated to a particular God  but often to a group of gods related to each other (Figure 5). There are however rare cases of altars dedicated to all Olympians in general or the Pantheon in its totality .
Technically the altar may vary in construction material or in shape and size  although for practical reasons a hardy natural material with resilience such as stone is preferable. The trapezoidal shape is preferential not only because it best serves the work to be done on the altar (placing of offerings, lighting of fires and cooking of sacrificial parts), but also because symbolically the shape recalls the mythical condition in which humans dined at the table with the gods . Commonly at the top of the altar and in the centre, a slotted recess is to be found known as "the escharis". In it the pan upon which the fire burns, known as the "epipyron", is placed (Figure 8). The participants in the ceremony stand in a circle around the altar, when the ceremony takes place in outer or rural sanctuaries or in a semi-circle when the ceremony takes place within a temenos (the courtyard in front of a temple where the altar is placed and which forms one complex).
The altar can be furthermore elevated upon steps thus creating a place for priests to stand upon known as the "prothesis". Its orientation is in relation to the Temple usually on an east west axis (East - Altar; Temple entrance - West).
Finally, a very important factor in our worship at the altar is our attitude towards it.
The altar must be maintained in good condition and must remain undefiled and without miasma as the slightest defilement will sever this link with the Gods making it inactive and rendering it into a simple construction without any religious function. In such a case the altar can be restored to its original state only after the successful completion of purification rites which require assistance from people with specialised knowledge . For this reason we must be properly prepared and careful when we approach the area of the altar.
Figures ( 1 - 8 )
 The well known phrase "for our altars and homes" illustrates the importance that is given to altars in the Hellenic community. Scenes of worship were depicted on altars as in Figure 1 and Ganymede offering wine to Zeus over the altar in Figure 3. From the dating of the finds, especially the latest dating for the altar found on Mount Lykaion, we can say that there is evidence for Olympian worship in combination with the existence of an altar as far back as 5000 years ago (also Neolithic and Mycenaean altars were discovered with inscriptions in Linear B').
 Thus the sanctity of the altar protects a seeker as soon as they touch it. Ref: the Case of Kyloneian Agos (the curse of Kyloneios) in Ancient Athens.
 As with the temenos or temple.
 Walter Burkert "Ancient Greek Religion" (Athens), 1993. This is not entirely true for residential altars established for family worship or for the altars at state buildings where the altar is directly related to the government building or a house; i.e. structures not as sacred as a temple.
 Usually the altar is established with the first sacrifice (or offerings) which are made on it.
 See "On household altars".
 Most public buildings in town had an altar. There were also altars in the market place and many other altars connecting the socio-political activity of citizens with the divine.
 While performing a similar function, altars to the chthonian and the deceased are not the same as other altars per se. They are pits or grates, known as an eschara, in which offerings are thrown and left to burn out.
 The term 'esoteric' refers to those features which, although essential for worship, are difficult to understand purely by observing only the exterior or mundane characteristics of findings studied in archaeology. Literature and philosophy is studied for a deeper esoteric significance.
 Usually we know to which God an altar dedicated through the inscriptions or the scenes engraved upon it. (Figure 4)
 For example the Altar of 12 Gods in the Athenian market and the altar in the Pantheon of Rome.
 Typical examples of the spectrum of possible variations of altars are those created by the deposits of ash in sanctuaries such as the Altar of Zeus at Olympia or Lykaion (Figure 6) and the monumental constructions of the Pergamon Altar (Figure 7) or that of Hieron II of Syracuse.
 Hesiod in "Works and Days" where we find an archetypal description detailing the method of sacrifice as done by Prometheus from preparation to execution. For a thorough study see Jean-Pierre Vernant & Marcel Detienne "La cuisine de sacrifice en pays grec" (Paris), 1979.
 A historical example is the case of the Kyloneian Curse when the Athenians were forced to bring the priest Epimenides from Phaistos in order to performing the necessary rites to cleanse the city of miasma. See the Wikipedia article on this. A mythical example is the miasma of the altar from the unburied body of Polynices in Sophocles' Antigone. The god Dionysus, patron of the city was summoned in this case to free them from the miasma.