Where can I locate a map of the public transit system in Frankfurt?

A map is available on page 17 of a long but helpful guidebook, accessible online in PDF format from RMV.  The guidebook also provides fare information in 12 languages.  RMV standards for Rhein - Main - Verkehrsverbund, which is the regional transit authority.

• How can one go between Frankfurt am Main International Airport and downtown?
• What public transportation is available to go between Frankfurt Airport and other major cities?

• Europe > Central Europe > Germany > Hesse > Frankfurt

• Transport > Municipal > Bus
• Transport > Municipal > Rail