Under the Pont d'Iena you can see the metal girders which were put in place in 1937, as well as showing the many arches over the River Seine. Daily updates at www.eutouring.com/pont_d_iena.html
This photo shows a view beneath the Pont de Bir-Hakeim, with the stone arches and metal designs. More photos to be seen at www.eutouring.com/images_pont_de_bir-hakeim.html
This photo taken beneath of the Viaduc d'Austerlitz, shows the stone and metal work which supports the Metro line above. You may also like www.eutouring.com/viaduc_d_austerlitz.html