I wanted to have an opera house with an interesting roof.
Nah, no famous building in mind, not at all.
Look at Herr Wotan's winged helmet and the other example.
It could work as a vintage version of the sydn... an opera roof and stands as a metaphor for the classic stageplays that might have happened inside the building.
(later in the process I had to change the roof a bit, to avoid it extending into the neighbours house several meters)