In 1857 Franz Joseph ordered the city walls demolished and a boulevard built on the cleared ground. The Ringstrasse is the result: a five-kilometre horseshoe around the old city, laid out on the glacis where nothing had been allowed to stand, and filled over the following decades with the buildings of a confident state. Each was given a historical style thought to argue for its function — Greek temple columns for the parliament, Flemish Gothic for the city hall, Renaissance for the theatre and the museums, an Italian humanist manner for the university. Art history took a term from it and calls the whole thing Ringstrasse style.
Walking the loop takes a couple of hours. Riding it is what locals do, though no single tram has covered the whole Ring since 2008, so the full circuit now means one change. Do it once in daylight for the architecture and once after dark, when the city hall, the parliament and the opera are floodlit and the traffic thins. The stretch by the city hall carries an ice rink in winter, films in summer and the largest Christmas market in the city.