ST. PAUL, Minn.—This northern city is trying to bring back workers, small businesses and a sense of security after the Covid-19 pandemic, not only to its downtown streets, but to a parallel world one flight up: a 5-mile warren of glassed-in bridges and passages through private buildings called the Skyway. “We’ve got two levels—and twice as much area that we need to make sure gets revitalized,” said Joe Spencer, president of the St. Paul Downtown Alliance in the city of about 320,000, which built the Skyway to allow people to get around downtown without going outside in Minnesota’s frigid winters.

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