King Louis XV vowed in 1744 that if he recovered from his illness he would replace the ruined church of the Abbey of St Genevieve with an edifice worthy of the patron saint of Paris. He did recover, and entrusted Abel-François Poisson, marquis de Marigny with the fulfillment of his vow. In 1755, Marigny commissioned Jacques-Germain Soufflot to design the church, with construction beginning two years later.
The overall design was that of a Greek cross with massive portico of Corinthian columns. Its ambitious lines called for a vast building 110 meters long by 84 meters wide, and 83 meters high. No less vast was its crypt. Soufflot's masterstroke is concealed from casual view: the triple dome, each shell fitted within the others, permits a view through the oculus of the coffered inner dome of the second dome, frescoed by Antoine Gros with The Apotheosis of Saint Genevieve. The outermost dome is built of stone bound together with iron cramps and covered with lead sheathing, rather than of carpentry construction, as was the common French practice of the period. Concealed flying buttresses pass the massive weight of the triple construction outwards to the portico columns.
The foundations were laid in 1758, but due to the economic problems in France at this time, work proceeded slowly. In 1780, Soufflot died and was replaced by his student, Jean-Baptiste Rondelet. The remodeled Abbey of St. Genevieve was finally completed in 1790, coinciding with the early stages of the French Revolution.