The Australian government apparently has bilateral agreements with a number of signatories to the Schengen Visa treaty that predate, and supersede, the standard 90/180 for traveling in the Schengen zone.
This Wikipedia article stipulates to the bilateral visa agreements:
According to this article, and some of the links I’ve followed to official documents, Australians are (potentially) permitted to travel within Schengen, and not have their stay in the following countries aggregate up to the 90/180, but be treated as separate periods, with the time permitted under the existing bilateral agreements.
Countries that appear to have bilateral agreements include:
In theory, this would permit an Australian passport holder to move relatively unrestricted around the Schengen zone for an almost infinite period.
For example, if I am permitted to be in Germany for 90/180, external to the Schengen treaty, I could, in theory, spend 90 days here, exit to Austria on the train, spend another 90/180, exit to The Netherlands by train, spend another 90/180, and then return to Germany, where my 180 days would have reset.
If you’re an Aussie, and have been traveling in Europe without any formal visa documentation, other than your passport, I’d love to hear from you. I’m attempting to plan out the balance of my time in Europe, and don’t want to fall foul with any officials. Getting a black mark on my passport would be highly undesirable.
Thanks in advance for your support