Saint Joseph's Oratory of Mount Royal

This guide to Saint Joseph's Oratory in Montreal starts with Brother Andre, who spent every cent he had saved cutting hair to open a small wooden chapel on this slope in 1904, and traces how it grew into one of the largest church domes on earth. It follows the engineers who poured that dome's concrete shell in a single nonstop push through a cold November in 1937, borrowing a centuries-old trick from a Florentine cathedral. Look up at the thinness of the shell before you learn how they managed it.