Secrets of San Francisco

Dozens of office buildings in San Francisco include privately owned public open spaces -- or "POPOS." Some are merely provisional, while others are hidden gems.

They're small and individual in character — dare I say lovable? — like single-family houses. And yet they shelter several families under one roof: maybe two, three, six or some other small number. Lots of cities have single-family houses that have been split up into apartments, but San Francisco's wooden multifamily houses were designed to have multiple units from the start.