… but non-German speakers might enjoy the images
The German Wikipedia page Mogontiacum (as usual handle with care) is a comprehensive one, though it says that it still needs editing ("bearbeiten"). It includes a list of the legions that were stationed in Moguntiacum.
The first image on the page is a section of the Tabula Peuteringiana (see also here and at livius.org) showing the area including Roman Mainz, courtesy Wikimedia Commons: click on image and look for the red arrow pointing to "Mongontiaco":
I'm still trying to find a list of the various types of pictorial symbols on the map. Assistance is greatly appreciated.