Question:  The House of Atreus Act I, released in 1999 is the first part of a metal opera inspired by the  only extant example of an ancient Greek theatre trilogy which won first prize at what festival?
Sentence (from "The House of Atreus Act I"): The metal opera was actually performed under the name "Klytaimnestra - The House Of Atreus" in European theatres from 1999 to 2001, with the production of the Memmingen Opera House company and Landestheater Production.
Relevant evidence: No