The conventions of ancient Greek theatre were entirely different from those of modern theatre. Along with the use of choral odes between scenes and stylised masks that completely hid the actors' face, the ancient Greeks also used a different type of performance space than theatre companies do today. Greek theatre was part of a major cultural festival celebrating the god Dionysus; as such, it was performed in a space designed as much for worship as for acting.
Theatre of Dionysus
Ancient Greek plays were performed in an amphitheatre called the Theater of Dionysus. This space was used exclusively for religious ceremonies celebrating and honouring Dionysus, among which were theatrical performances. Its stage area was called the orchestra, meaning the "dancing place"; it was a circle with a diameter of 64 feet. In the centre of the orchestra was the thymele, the altar to the god. Surrounding the orchestra in three directions was the theatron, or "seeing place." The theatron was a hillside covered in benches for the audience, with room for about 15,000 people.
The back of the orchestra, the one side that did not face the theatron, housed the skene, or "hut." The skene was an enclosure about 100 feet long that was probably originally used as a dressing-room for the performers. As the art of theatre developed, it came to be used more and more as scenery. The skene had three doors to the orchestra; its edges bent forward into the orchestra like wings. Between these wings was a raised step that was used as a second level of the stage.
The Theater of Dionysus was too large for realistic sets or for many props: they would not have been visible to the audience. The earliest Greek plays were closer to religious rituals than to theatre and probably did not have any sets at all. When painted sets did come into use, they were stylised representations of familiar locations that audiences expected to see in plays, like palaces, forests and temples. These were erected between the doors on the skene.
Ancient Greek plays required a few special effects, like characters flying and gods descending. For this the ancient Greeks used a crane, housed on top of the skene, to lift the actors when necessary. Horses and chariots would also come on stage with the protagonist the first time he entered, as a signal to the audience that this was the hero. For actions that could not be realistically performed live, such as Oedipus gouging out his own eyes, the actors would exit into the skene and leave the door open behind them. This allowed their voices to travel to the audience while keeping the action itself out of sight.