The theatre of Herodes Atticus, also called as Odeion of Herodes Atticus, is a stone theatre structure located on the south slope of the Acropolis. It was built in the 2th century by Herodes Atticus in memory of his wife. It was originally an amphitheater with a wooden roof, and was used as a venue for music concerts with a capacity of 5,000. In 1950, the Odeion of Herodes Atticus restored a is now used as an open-air concert hall.
More photos of the may be found on the Wikimedia Commons server.