Salzburg - City of 7 festivals

The number 7 contains magic: In the medieval it was a symbol for grace and peace, because it consists of the number three, the symbol of Trinity and the number four, the symbol of the world, the four elements, the four wind directions and the four points of the compass.

There are the Seven Wonders of the World, the seven archangels, the creation of the world in seven days and wasn't Rome built on seven hills?