perhaps take an oxygen mask....I went to Austria last year and the whole population smokes! In restaurants too....bleh!
We did an ice-cave tour...had to walk up a big hill (maybe 20min) and then a million ice steps inside the cave...was a work out but worth it.
Also did the 'Sound of Music' tour much to DH's dismay! That was fun....though you find out that only about 5% of the movie is true...the rest is Hollywood! And the Autrians hate the movie...so don't skip about singing about Maria!
Birkenstocks are cheap so get some!
Enjoy, and don't forget to have some beef goulash for me!