Legend has it that the Duke of Savoy, Vittorio Amedeo II and Prince Eugene of Savoy watched from the hill of Turin, besieged by the French-Spanish. Vittorio Amedeo, kneeling before an old pier, swore that, if victorious, would build a tribute to Holy Mary.
After building a monument to the victory of the battle, Vittorio Amedeo, later crowned King of Sicily, split the vote and gave the design of the building to Philip Juvarra in 1711.

The Basilica is circular, measuring 75 meters high, 51 long and 34 wide. The stately facade is topped by a cupola and flanked by two twin bell towers. The building stands on a platform which can be reached by climbing the balustrade that is three steps from the yard. Inside the marble floor is a rose coloured circles.
The sacristy is all covered with walnut cabinets designed by the Juvarra.
The altar of SS.Annunziata, by Bernardino Cametti by  Gattinara, with the Blessed Amedeo di Savoia in attitude of prayer and battle, to remember the events of 7 September 1774.

In 1706 Francis Martinez, nephew of Juvarra, turned the basement into a mausoleum.
Among these there are the coffins Vittorio Amedeo II and Charles Emmanuel III, Carlo Alberto and Vittorio Emanuele I.