Mainz, at the confluence of the Rhine and Main rivers, was founded by the Romans in the 1st century BC. It became an important city in the 8th century AD as part of the Holy Roman Empire, Mainz is famous as the birthplace of Johannes Gutenberg, the inventor of a movable-type printing press,. Mainz is notable as a transport hub, for wine production, and for its many rebuilt historic buildings.
Historically, Mainz was just beyond the limits of the Norman and Danish Viking raiding and trading in the Rhineland area from 864 until about 885. Never the less, the city walls were reinforced due to the Viking threat and the Vikings lost a battle near Mainz in 882.
Saga Asia Stage 3 starts here and proceeds up the Main River to Regensburg, Germany. While transiting 50 locks or so along the way might seem onerous one could say they are much preferable to physically portaging a 20-meter ship!