What's your favorite opera aria, chorus or orchestral piece, and why?

Portland Opera's upcoming BIG NIGHT Concert will feature opera's greatest hits.  What's your favorite opera aria, chorus or orchestral piece, and why? 

Comments:

My favorite aria is "Der

My favorite aria is "Der Hölle Rache kocht in meinem Herzen" sung by the Queen of the Night in Mozart's The Magic Flute. Beautiful and it is one of the more difficult arias I think. The women who can sing it well deserve to be worshipped as goddesses! LOL