Rosace Room

View, including partial cutaways and cross-sections, of the rosace room located in the basement of the central telephone office and exchange of the avenue de l'Opéra in Paris. The "rosaces" were made of the wires connected to satellite switches. A cross-section view on the right shows the proximity of the sewers, through which the cables ran, and, above, the avenue de l'Opéra. 

The caption reads in the original French: Salle des rosaces du bureau central de l'avenue de l'Opéra.