What is the name of the river that had a bridge in the capital of Britannia Superior?
Britannia Superior:  Britannia Superior was the southern province of the two, with its capital at Londinium, or what is today London. Londinium:  Its bridge over the River Thames turned the city into a road nexus and major port, serving as a major commercial centre in Roman Britain until its abandonment during the 5th century.
River Thames