It's a joy to explore Vienna's center on foot. You don't have to worry too much about traffic, and this slow pace enables stopping every 5 minutes or so - to stare in awe at the buildings. Almost every one of them has special ornaments: iron balconies, circular towers, frescoes, statues, and marble pillars.
The City Hall ("Rathaus") is a relatively recent addition to Vienna's splendour (19th century). This huge building at the Ring is in neo-gothic style, and this way blends in very easily with its surroundings. Another highlight for me was the "Am Hof"-square - this is where the medieval predecessors to the Habsburg family had their main seat. Nowadays the fire brigade inhabits one of the magnificent buildings here.
Vienna was a pleasant surprise. Having visited Prague and several German cities, Vienna does stand out because of its overall character: its cleanliness, the condition of its buildings and the general chic atmosphere.