Notre-Dame is a basilica, not a cathedral — a distinction older accounts of it routinely get wrong. Montreal's Catholic cathedral is Mary, Queen of the World, a few streets away in the business district.
It stands on Place d'Armes in Old Montreal, and its interior is the most extraordinary thing to look at in the city.
Notre-Dame was commissioned by the Sulpicians in 1823 as a parish church, and the architect they chose was James O'Donnell — born in Ireland in 1774, working out of New York, and a Protestant. The cornerstone went down in September 1824 and the church opened in 1829. O'Donnell converted to Catholicism shortly before his death in January 1830, and he is the only person buried in the crypt.
The twin towers came later, finished in 1841 and 1843 to designs by John Ostell. For about fifty years after it opened this was the largest church in North America. Accounts that name St Patrick's in New York as the building that overtook it are guessing; no source supports the attribution, and it does not survive comparison of the two interiors.
What visitors come to see was installed between 1872 and 1880 by Victor Bourgeau, working with the parish priest Benjamin-Victor Rousselot, and it replaced O'Donnell's scheme for a practical reason: his great east window sat directly behind the altar and backlit it, so the congregation spent services staring into the glare. Bourgeau took his cue from the Sainte-Chapelle in Paris.
The west tower holds Le Gros Bourdon, nicknamed Jean-Baptiste, cast in the 1840s and weighing about eleven tonnes. Accounts saying "over twelve tons" are using American short tons; in British measure it is a little under eleven long tons. It is rung only on special occasions. The east tower carries a carillon of ten bells.
The Chapelle Notre-Dame-du-Sacré-Cœur burned in an arson attack in 1978 and was rebuilt, reopening in the early 1980s. Behind its altar is a single monumental bronze by the Quebec sculptor Charles Daudelin — a reredos some sixteen metres high weighing twenty tonnes, not the set of thirty-two cast panels that older accounts describe.
The chapel is known locally as the wedding chapel, and it is where a great many Montreal weddings happen.
Entirely absent from older accounts, because it did not exist: Aura is a light-and-sound work staged inside the basilica by the Montreal studio Moment Factory, running in the evenings since 2017. A mechanical system plays the Casavant organ live as part of it. Visitors walk past illuminated stations and then sit for a projection across the walls, vault and altarpiece, the whole thing lasting a little over three quarters of an hour.
It needs a separate ticket from the daytime visit, and booking ahead is sensible. For many people it is now the reason they come.
Daytime sightseeing is now ticketed rather than run on the donation basis older accounts describe, with a self-guided route of a couple of dozen marked points and bilingual panels. A combined ticket covering the day visit and Aura is also sold. Major restoration work has been under way since 2020 and parts of the building may be screened.
It remains a working parish church with Masses and private prayer, which is worth bearing in mind — the sightseeing hours and the hours of worship are not the same thing.
The basilica is at 110 Notre-Dame Street West, on Place d'Armes in Old Montreal; the Metro station is Place-d'Armes. Saint Joseph's Oratory up on the mountain is the city's other great church and is nothing like it. General practicalities for the city are on the Montreal page.