I was blown away by how beautiful it was, and would go as far to say that it rivaled Versailles in its ornateness.
Everywhere you looked, there were intricate details, glowing chandeliers, gold-leafing and frescoes.
There was also a library that looks exactly the same as it did 100 years ago. It is part of a little known set of libraries in Paris called les bibliothèques spécialisées. As the name suggests, they each have their own specialty: architecture, music, theater, etc. (Some of the others are as beautiful as this one.) And with a few exceptions, they are open to the public, as long as you sign up for the bibliothèque spécialisée card.