Hofburg Palace is a MUST-visit in Vienna. Chances are, if you're going to visit a museum as a…read moretourist, at least one of them will likely be at Hofburg Palace or within its vicinity. The Sisi Museum was one that I visited, and all day long, the palace grounds are teeming with tourists. Even if you don't enter the palace, you can walk through the grounds, enjoy the garden, people watch, and enjoy watching the horse-drawn carriages.
Baroque architecture heaven!