Does Mainz train station have luggage storage?
 

Hi there, am thinking about leaving my suitcase at the Mainz station for a couple of hours while I run around the town, is thiat possible?

Big stations in Germany all have luggage lockers. In Mainz, they cost €2 or €3, depending on size. They take coins of 50 cents or €1.
www.bahnhof.de

In case you don't speak German, here's the website in English:

http://www.bahn.com/i/view/USA/en/index.shtml

thanks for that !

Yep, we used them in 2009 for our luggage. The key is usually to have coins on you to pay for them.