I am traveling to Austria in September to celebrate my 50th birthday. It is my first time visiting Austria and not sure where I should visit. I am planning 2 days in Vienna and 2 days in Salzburg and have 2 more days left to explore. Any suggestions on where I should visit, in travel books they suggest, Melk, Graz and Hallstatt? I would appreciate any advice on how to plan my trip! Thanks!