There is so much to do and see as you will see in the reviews. As there is enough written about the places there, I will use this space for a litte information on the Habsburg family.
If you will come to Vienna and visit some sights you will sure hear the name Habsburg. This is not surprising as they reigned Austria for more than 600 years and brought fame and fortune to the country. So I don't want to bore you with history. But if you want to pre-inform yourself before the trip, just google the Habsburg family or read about them. You will find names like Franz Josef and his wife Sisi or Maria Theresia and her daughter Marie Antoinette being part of the long heritage of Habsburg family.