There is 5 rooms like this under the big dome of the opera Garnier.

Panoramical vision of Garnier opera rooftops

The great dome of the Opera Garnier, home to several dance halls, each with its own piano. The most prestigious occupies the entire area under the green dome. The floor of the ballroom is inclined to replicate that of the theater. A sloping floor allows the public to see the choreography. For some shows, you need a flat surface. It then adds a platform.

Source: words collected from a former manager of the opera.

Behind the scenes at the Opera Garnier in Paris.

Around the Garnier opera, all buildings are height limited. So the view from this crane is very unique!

If you look closely, you can see a security guard on the picture.

In the main repetition danse room, under the big dome.

panoramical view of the opera.