Characteristics of the buildings

The Ancient Theatre of Delphi.

The plays had a chorus from 12 to 15^[10] people, who performed the plays in verse accompanied by music, beginning in the morning and lasting until the evening. The performance space was a simple circular space, the orchestra, where the chorus danced and sang. The orchestra, which had an average diameter of 78 feet, was situated on a flattened terrace at the foot of a hill, the slope of which produced a natural theatron, literally "watching place". Later, the term "theatre" came to be applied to the whole area of theatron, orchestra, and skené. The coryphaeus was the head chorus member who could enter the story as a character able to interact with the characters of a play.

A drawing of an ancient theatre. Terms are in Greek language and Latin letters.

The theatres were originally built on a very large scale to accommodate the large number of people on stage, as well as the large number of people in the audience, up to fourteen thousand. Mathematics played a large role in the construction of these theatres, as their designers had to be able to create acoustics in them such that the actors' voices could be heard throughout the theatre, including the very top row of seats. The Greeks' understanding of acoustics compares very favourably with the current state of the art. The first seats in Greek theatres (other than just sitting on the ground) were wooden, but around 499 BC the practice of inlaying stone blocks into the side of the hill to create permanent, stable seating became more common. They were called the "prohedria" and reserved for priests and a few most respected citizens.
In 465 BC, the playwrights began using a backdrop or scenic wall, which hung or stood behind the orchestra, which also served as an area where actors could change their costumes. It was known as the skênê (from which the word "scene" derives). The death of a character was always heard behind the skênê, for it was considered inappropriate to show a killing in view of the audience.^{[citation needed]} Though there is scholarly argument that death in Greek tragedy was portrayed off stage primarily because of dramatic considerations, and not prudishness or sensitivity of the audience.^[11] In 425 BC a stone scene wall, called a paraskenia, became a common supplement to skênê in the theatres. A paraskenia was a long wall with projecting sides, which may have had doorways for entrances and exits. Just behind the paraskenia was the proskenion. The proskenion ("in front of the scene") was beautiful, and was similar to the modern day proscenium.
Greek theatres also had tall arched entrances called parodoi or eisodoi, through which actors and chorus members entered and exited the orchestra. By the end of the 5th century BC, around the time of the Peloponnesian War, the skênê, the back wall, was two stories high. The upper story was called the episkenion. Some theatres also had a raised speaking place on the orchestra called the logeion.