Introduction to the hollow gallery: The highest level of the building is the hollow gallery. On the gallery are two towers that can view the entire Paris. On the gallery, there is a row of carved sculptures of fire-breathing monsters, vampires, devils, etc. in different shapes. In the design of the arched stone railings, Valéry Le Duc gave full play to his imagination: on those stone railings, he created an illusory world composed of many gods, demons, and elves. The faces and expressions of these monsters Weird and cold, looking down at the misty city below; there are also some elves that look like birds, but with strange wings. They are either behind the spire or on the edge of the railing, looming in every corner of the top of the church. They have been squatting here quietly for hundreds of years, thinking about the fate of the people in Paris beneath them.