The Ponte dell’ Ammiraglio (Admiral’s Bridge) in Palermo, Sicily, built from 1125-1135 (or 1113, according to the Italian Wikipedia), is one of the oldest surviving post-Roman era arch bridges in Europe.  The bridge has been restored and surrounded by a new park, but also being surrounded by busy Sicilian roads, cut off from its original purpose, and outside the main tourist area, it is little visited.

There is also little information about this bridge on the Internet (at least in English), but I did find a lengthy discussion on the history of pointed arches, and where they came from, which is well worth a read at:

Nexus Network Journal (architecture and mathematics on-line)

Thanks to the comment from Pier below, a You tube video of an event on the bridge: