Underground Cities: Travel below the surface of five American towns

City Hall Station in New York

On your next trip to the United States, you can visit the attractions everyone can see or you can go underground. By “underground,” we don’t mean secret, although some of the places on this list certainly seem so, from San Francisco’s speakeasies to the backway into NYC’s City Hall Station. We mean literally underground — as in beneath the surface, below where many travelers…