Voynich manuscript expert Richard SantaColoma started interesting discussion at the VMs list about the castles pictures on the 9-rosette. He shows examples of castles that are completely made-up with no connection to real structures (all of them in forged manuscripts). I agree with him that the Voynich manuscript being a forgery is a possibility (especially having in mind the period during which it was discovered in modern times). However, it is irresistible fun to browse through pictures of European medieval castles looking for clues (much like looking at wild flowers - it just makes me happy).
So here comes the castle of day.
Many drawing in the VMs have details that could be just mnemonic reminders for the author. So I thought - what if the 'volcano' on the 9-rosette is a clue for volcano - but not necessary fuming one.
The castle on the picture is actually the facade of Maria Laach Abbey (established in 12th century), which is situated on the banks of Laacher See in Germany. The See is in fact a volcanic crater lake. So there you have it - castle next to volcano.
The comparison is just for fun. The ghibelline merlons in the 9-rossette scream more 'Italy' than 'Germany' (which is ironic since they are supposed to demonstrate allegiance to the Emperor), the sketches of the castles may not be based on real buildings, and inch distance between drawings on the 9-rosette may be hundreds of miles on the map.