St. Stephan’s Cathedral and the Imperial Palace are the two major attractions in Vienna city center. The Cathedral itself was not that memorable, although it does offer a good view of the city from the top of its tower. The business area between the Cathedral and the Palace is more interesting, having shops and restaurants mixing in mostly historic buildings.
On the other hand, Hofburg offers quite a few things to see. The Imperial Apartments have displays on stories and history of the emperor Franz Joseph (supposedly a good hardworking emperor); the Sissi Museum has some more interesting stories about empress Sissi (we were so interested that we actually took our time to read most of the displays); and the Imperial Treasury (some impressive crown jewels)
One problem with visiting the Hofburg is that they have separate admission to different buildings in the palace. So even though I had put down the National Library and the Spanish Riding School in our plan, we ended up not seeing them (save money, save time). Another disappointing thing is that most places there do not allow photo taking, so I don’t have a lot of pictures of what we saw.