Notre-Dame de Montréal was built between 1824 and 1829 on the Place d'Armes in what was then the Catholic heart of a British-ruled, French-speaking city. The architect was James O'Donnell, an Irish Protestant from New York; he converted to Catholicism the year before his death so he could be buried in his own creation. The Gothic Revival exterior was radical for North America in 1829 — no other building on the continent looked like it.
The interior is the reason to visit. Victor Bourgeau's redesign in the 1870s filled the sanctuary with carved walnut, gilt-leaf painted details, and the royal-blue ceiling studded with 24-karat gold stars that's become the building's signature image. The stained-glass windows — unusual because they depict scenes from Montréal's religious history rather than biblical ones — were installed 1929–31 by Francis Chigot of Limoges. The Casavant Frères organ has nearly 7,000 pipes; Celine Dion was married in this church in 1994.
AURA is the evening product. Produced by Moment Factory (Montréal's own immersive-media studio), it projection-maps a 45-minute orchestral show onto the interior — the ceiling stars come alive, the walls ripple, the sanctuary becomes a stage for a wordless narrative. It sells as a separate-ticket evening experience, distinct from the daytime self-guided visit. The daytime interior is architecture and history; AURA is what Moment Factory does to architecture with light. Two different visits.