The oldest standing bridge across the Seine is Pont Neuf, "New Bridge", of course. It's the setting for the remarkable film Les Amants du Pont-Neuf:

https://youtu.be/y2OjjtY1A80

This is what I think of whenever I see the Seine in the news.

Internet Archive has the full movie:

https://archive.org/details/les.-amants.-du.-pont-neuf-1991