Hi all, we will be in Paris in late March. We would like to visit the Paris Opera (the old one) and cannot seem to find any straight answers on the web about

-whether we can tour it
-When its open
or
-how much it costs

Does anyone know? Any info or help on this would be much appreciated.

Also, my 7yo daughter wants to know if the Paris Opera really has a lake under it, like In the Phantom book.....anyone know?

merci