Why did Attila spare Paris?

Since antiquity, the name of Attila, the King of the Huns, terrified the Euro-peans as much as it made proud his fellow countrymen.  There are those who consider him a wild barbarian, there are those who think of him as a great hero.  Yet, what are the real tracks left by Attila's soldiers in Europe in addition to the frightening sound of his name?

Who and why built a monument for Attila in France? Why did Attila spare Paris? How does the steppe spirit help the “modern nomads” of France?