On 11 June 1711, the church was formally completed with the solemn deposition of the relics of Saint Gaudenzio in the reliquary, which had been stored in St. George's Chapel since 1552.

Planning for the Basilica's most notable feature, its huge cupola, began fifty years later, once sufficient funds had been raised for the purpose by an increase in taxes.

In 1855, Antonelli submitted an even more ambitious plan than the original, increasing the cupola's projected height from 65 to 75 meters, and by 1858, funds had been mustered to continue works.

By this time, most of the cupola had already been completed, but the battles over cost had prevented the dome from being built, and Antonelli devoted most of the next ten years to the Mole Antonelliana in Turin.

In the following years the church began to show signs of structural failure under the weight of the cupola, which was, moreover, already discernible during the early stages of construction.

In recent years a series of sophisticated alarm systems have been installed inside the building to monitor any dangers of subsidence, cracks or oscillations.