Leaving the narrow streets of the Old town, the appearance of Vienna changes radically as you reach the Ring, the ring of boulevards around the city. The city's old fortifications became the site of the most extensive urban development programme ever to be undertaken in the imperial capital, as it was at the time. Between 1857 and 1913 a series of imposing public buildings were erected, their façades each in a particular «historic» style, opposite each other on either side of vast parks.