The architect of Notre-Dame Basilica of Montreal was so moved by the building he was creating that he converted to Roman Catholicism partway through. James O'Donnell, an Irish-American Anglican from New York, never lived to see the towers finished in the 1840s, but he is the only person buried inside, which seems a fair trade.

Commissioned by the Sulpicians in 1824, the basilica seats four thousand and was once meant to hold ten. Its vaults are deep blue and scattered with golden stars; the stained-glass windows skip the usual biblical scenes and tell the religious history of Montreal instead. Celine Dion was married here in 1994. Pope John Paul II raised it to basilica status in 1982.

VoiceMap's self-guided audio tours circle Place d'Armes and trace the Sulpicians' founding role in the city, using the basilica to explain how a Paris-born religious order shaped Old Montreal.