The Odeon of Herodes Atticus is a stone theatre structure located on the south slope of the Acropolis of Athens. It was built in 161 AD by Herodes Atticus in memory of his wife, Aspasia Annia Regilla. It was originally a steep-sloped amphitheater with a three-story stone front wall and a wooden roof, and was used as a venue for music concerts with a capacity of 5,000.

Reference from Wikipedia: http://en.wikipedia.org/wiki/Odeon_of_Herodes_Atticus