Not many years ago, downtown St. Louis was, like most old American downtowns, a void, dreary and disheartening, a place where respectable people worked, bums lived and almost nobody strolled. Given that lifelessness, the city's attempt to create a heroic modern monument to itself in 1965, Eero Saarinen's arch beside the Mississippi, came to seem like self-mockery: a pure, gorgeous steel span rising from a dying downtown and a forgotten riverfront, a giant logo erected as a wishful substitute for authentic urban reconstruction.
Lately, however, the core of St. Louis is being redeemed for real. The Old Post Office, a grand...