This Chambered Nautilus of a staircase with the worn marble steps is found in Bibliothèque Nationale de France (BnF) on Rue de Richelieu. Built in 1868, the library held the largest collection of books in the world by the turn of the 20th Century. The elegant grand staircase is in another section of this enormous library complex.
On another day I will post the "forbidden photographs" taken as Peter (of Peter's Paris) kept watch...
Bibliothèque National de France - Richelieu
5, rue Vivienne