There is a wonderful article at the UNESCO site concerning the city of Salzburg and below you can find a part of their article and of course the link to the original text of the UNESCO in all languages.
‘Outstanding Universal Value’
Salzburg is an outstanding example of an ecclesiastical city-state, peculiar to the Holy Roman Empire, from Prussia to Italy. Most disappeared as political and administrative units in the early 19th century and adopted alternative trajectories of development. No other example of this type of political organism has survived so completely, preserving its urban fabric and individual buildings to such a remarkable degree as Salzburg.
Salzburg is the point where the Italian and German cultures met and which played a crucial role in the exchanges between these two cultures. The result is a Baroque town that has emerged intact from history, and exceptional material testimony of a particular culture and period. The centre of Salzburg owes much of its Baroque appearance to the Italian architects Vincenzo Scamozzi and Santino Solari.
The Salzburg skyline, against a backdrop of mountains, is characterized by its profusion of spires and domes, dominated by the fortress of HohenSalzburg. It contains a number of buildings, both secular and ecclesiastical, of very high quality from periods ranging from the late Middle Ages to the 20th Century. There is a clear separation, visible on the ground and on the map, between the lands of the Prince-Archbishops and those of the burghers. The former is characterized by its monumental buildings – the Cathedral, the Residence, the Franciscan Abbey, the Abbey of St Peter – and its open spaces, the Domplatz in particular. The burghers’ houses, by contrast, are on small plots and front onto narrow streets, with the only open spaces provided by the three historic markets. Salzburg is rich in buildings from the Gothic period onwards, which combine to create a townscape and urban fabric of great individuality and beauty.
Salzburg is also intimately associated with many important artists and musicians, preeminent among them Wolfgang Amadeus Mozart.’
Original Link: UNESCO SALZBURG