The graceful curves of this wrought iron and glass awning are typical of art nouveau detail.
The pattern on the stones resembling coral are called "vermiculation" as it mimics the trail of worms in soft soil. This is one form of an architectural technique known as "rustication" which has been in use at least since the rennaissance period. You may have noticed this same pattern on the Louvre palace and Haussmannian buildings around Paris.
This elegant home which sits inside the gates of Parc de Monceau has a stunning main entrance in the courtyard. This is just the "back door."
5, ave Van Dyck