Sydney Opera House, to me, is the finest example in the world of 20th century architecture (admittedly a low bar). People will be visiting this 500 years from now and will still admire it for its beauty, grace and style. A fascinating story of how it was designed, redesigned, and finally resulted in this outstanding structure.
I took a tour during the day and saw Don Giovanni in the Opera theater. The tour was fascinating, but I recommend reading up on it before you go. The attention to detail and the craftsmanship are amazing is such a relatively new structure. They obviously take great care in maintaining and upgrading the facility.
The opera was a first class performance. The acoustics were wonderful, as was the staging.
Two heads ups: they say come as you are for the Opera. It is true there were tuxes and there were blue jeans, but i did feel under dressed without a coat and tie. (No choice: no room in the suitcase during my 21 day adventure). Also, only beer and wine during intermission. :(