A trip behind and beneath the street-level skin of the city on the hidden paths of industrial history and once-and-future transit. A trip behind and beneath the street-level skin of the city on the hidden paths of industrial history and once-and-future transit. A trip behind and beneath the street-level skin of the city on the hidden paths of industrial history and once-and-future transit. A trip behind and beneath the street-level skin of the city on the hidden paths of industrial history and once-and-future transit.