The largest Opera House in the world according to the number of seats is the Metropolitan Opera House in New York City. It has 3,800 seats and more than 300 spaces for standing room. It's followed...
the sydney opera house is called the sydney opera house because opera is song in the building and because of its great views.
it is 161,542,952 tons heavy
I think it is around 2000m long I think
Wood, metal & other substances