The Basilica di Superga was built to satisfy a vow made by Vittorio Amedeo II made in front of the statue of the Mother of Graces during a difficult time for the Savoy dynasty. In 1706 Turin was invaded by the French troops of Luigi XIV who ambitiously hoped to transform Piedmont into a French province, but found a fierce resistance on the part of the Duke Vittorio Amedeo II.

The story claims that on the 2 September 1706 the Duke, along with Prince Eugenio, climbed the hills of Superga to examine the battlefield from a great height. The small church at the top of the hill served the few parishioners of Superga. In front of the statue of the Madonna, the Duke made a vow: if he obtained victory against the French, he would erect in that place a large church in his honour.

When descending the hill the two princes discussed their plan of battle. On the morning of the 7th September at 10 o'clock the fighting began. The battle was bloody and terrible but the Piedmontese army had the better of their French counterparts who were defeated. Turin was free and Piedmont maintained it's liberty.

The Duke Vittorio Amedeo II assumed the crown of Sicily and then Sardinia and in 1717 laid the first stone of the glorious temple vowed in the honour of the Madre del Salvadore - The Savour of Turin. It was necessary to lower the hill by forty metres, and after having demolished the existing church, sold to the King by the Council of Turin. The project to build the Basilica was handed to the messinese abbot Filippo Juvarra, who produced an outstanding piece of architecture. The Basilica was opened to the public after 14 years of work on the 1st November 1731.

(Source: basilicadisuperga.com)