No text, but a visual code

[Jorge_Stolfi]

In the center is a T‑O map

We already went through this.  The central element is not a T-O map: the orientation is wrong.  Rather, it is a diagram that was used (devised?) by Oresme to illustrate the creation of the word according to the Bible: the bottom half is the Biblical "waters below", the top half is dry land, divided into wilderness and populated areas.  Several copies of that diagram were posted to this forum somewhere.

surrounded by a blue cloud with stars inside it.

Comparing this illustration with the Oresme diagram above we can see that the squiggly border of the starry area is a mangled reproduction of a cloudband that separated the Earth (the "inverted T-O map") and the heavenly bodies from the Biblical "waters above" -- the vast ocean that lies beyond the sky, whose drips are the rain, and, when God "opened the gates", came down as the Flood. 

Spirals emanate from the T‑O map.

I did not see any version of Oresme's diagram with anything like these spirals.  They may be an original contribution of the VMS author.  Or maybe he had an "enhanced" version of Oresme's that we do not have.

For example, the most banal assumption about the Rosettes is that it is a map of some Italian region. This version is SUITABLE and LOGICAL, because we can associate it with balneology, where (in the context of the same theory about the periplus with a list of hot springs and lakes) the same geographical features or objects from the same region are depicted.

Whoa, this is far from a "banal" interpretation.  I know of no region of Italy that has a geography remotely similar to that chart.

There are two active volcanos on the big fold-out, sticking out of the NE and SE rosettes.  There are half a dozen volcanos in Italy that  were active in historic times; including three near Naples, which are related to the many thermal springs in that area.  That would be consistent with the "balneological" interpretation.  However, the geography of that region is nothing like "nine islands".

Venice is a bunch of islands connected by bridges.  But the islands have complicated shapes and the channels are rather narrow.  And there is no volcano anywhere near that place.

Maybe the fold-out is a map of part of the Greek archipelago.  There are lots of islands there, and a couple of historically active volcanoes.  But no bridges between islands... 

But the most banal explanation is that the fold-out is a map of an imaginary place.  Like the maps that I liked to draw when I was a kid...

All the best, --stolfi