October 26 (Monday) is Austria National Day. This holiday celebrates the anniversary of Austrian neutrality, but, ironically is a holiday that showcases the Austrian military.
What should you know about this holiday?
Shopping - On a practical level, as this is a public holiday, all shops, schools, banks, post offices are closed. If you happen to need groceries on this day, go to the Billa at Praterstern, the Spar Pronto at Wien Mitte or Hauptbahnhof, or the Billa Corso at Neumarkt (warning, they will be very crowded and not all items are available for purchase).
Special Events - There is a huge military show at Heldenplatz open to the public in case that is your thing. There will be laying of wreaths and lots of Austrian flags.
Free Museum Admission - Several national museums are free on this day. The Austrian National Library (Prunksaal or State Hall) and its associated museums (Globe, Papyrus and Literature Museums) are free. The Museum of Applied Art (MAK) is free and it is one of my favorites. The Military History Museum (HGM) is also free - exhibits are described in English.
Enjoy!