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In the top left of the picture to the right you can just make out the similar shrines at the back of the Theatre of Dionysus in Athens. These seem to be under repair at the moment.
Left is the theatre at Segesta (3rd Century BC), in the northwest of Sicily. Like many ancient theatres the theatroi [triangular segments of seating] have been refurbished and the theatre is used as an outdoor venue during summer evenings. Though in many ways unfortunate in terms of authenticity, the refurbishments do at least give a practical definition to the orchestra [semicircular performance surface] and to the paradoi [entrance / exit corridors to the side of the stage].
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An arial view of the Theatre of Dionysus, in Athens. The triangular theatroi are particularly apparent in this view.
The pictures above are of the theatre on the island of Delos (3rd century BC). The island was the birthplace of Apollo and Artemis and is like Delphi in that the site is largely dedicated to temples and there are few practical buildings. On the part of the island that the theatre is in there is a fairly large network of later Roman buildings many of which have mosaics that are in one way or another evocative of drama (e.g. Dionysus riding a leopard). As you can see this theatre has not been recently renovated to house performances (the island is in the middle of nowhere) and offers some glimpse of how the other ruins might have looked before reconstruction.
In the Old Theatre, Fiesole (April, 1887)
by Thomas Hardy
I traced the Circus whose gray stones incline
by Thomas Hardy
I traced the Circus whose gray stones incline
Where Rome and dim Etruria interjoin,
Till came a child who showed an ancient coin
That bore the image of a Constantine.
She lightly passed; nor did she once opine
How, better than all books, she had raised for me
In swift perspective Europe's history
Through the vast years of Caesar's sceptred line.
For in my distant plot of English loam
'Twas but to delve, and straightway there to find
Coins of like impress. As with one half blind
Whom common simples cure, her act flashed home
In that mute moment to my opened mind
The power, the pride, the reach of perished Rome.
This is the an aerial view of the theatre at Delphi (originally built in the 4th century BC and enlarged in the 2nd, potentially in 159 BC). At the back left of the picture you can make out the remaining columns of the Temple of Apollo, where the Pythia breathed her criptic noises for the priests of Apollo to turn into hexameter, with the treasury building on the level below on the right hand side.
This is the Roman theatre (there may have been an earlier Greek theatre on the site but there is no real evidence to suggest it). What is interesting about this building is the way that the city has just ignored it as it built up all around it. It is not visible from the street.