Bridge was built by Gustave Eiffel
The bridge used in the film was built by Gustave Eiffel in 1881-1884. This didn't surprise me when I thought about it...
http://www.cantalpassion.com/viaducde.htm
It is still in use today as a railway bridge. As you see in those photos, there are actually quite a few buildings in the area that, in the movie, are just off-camera.