Here in Rome (Italy) there are maybe two bridges which can better describe the contrasts between old and new constructions. 

For the old ones, Ponte Milvio is the one that best represents the ancient technologies. First built by ancient romans, it was the theatre for many battles of the past and was also partially destroyed and rebuilt. Here you can find more informations:

https://en.wikipedia.org/wiki/Ponte_Milvio

Another bridge which now represents the new architecture in the city is the "Ponte della Musica", very close to the first one. It is a 200 m single span arch bridge. It was designed by Buro Happold and it is very beautiful. Here you can find some pictures and figures.

http://www.archdaily.com/179789/ponte-della-musica-buro-happold

https://en.wikipedia.org/wiki/Ponte_Milvio

http://www.archdaily.com/179789/ponte-della-musica-buro-happold