(And, of course, has never been destroyed by a fire.)

The real Palais Garnier, which the Opéra Populaire is based on, also hadn't been completed yet.

Artistic License History: In Real Life, Paris in late 1870 was under heavy siege by the Germans, whereas in the film there's nary a hint of the Franco-Prussian War.

Giry, and both The Phantom and Christine. In the original musical, there was a confrontation between Raoul and the Phantom in the graveyard, but it never got this violent the Phantom was implied to be more interested in trying to scare Raoul off than kill him, and Raoul didn't try to capture the Phantom because he knew he'd have a better opportunity later during the performance of Don Juan Triumphant. only to let him go when Christine asks him to spare his life, rather than taking him into custody, which was what he wanted to do by this point. Raoul wins and is about to kill the Phantom.

Adaptation-Induced Plot Hole: This movie adds a scene where Raoul and the Phantom have a swordfight in the graveyard where Christine's father is buried.

Christine's backstory gets a little more development as well, showing how she came to the opera house as a young girl.

It's explained how Madame Giry came to know and unofficially 'work' for the Phantom when she was a teenager and he was presumably around ten, she helped him escape from a travelling fair where he was abused and exhibited as a sideshow attraction, and hid him in the opera house.

Phantom of the opera costume reference