A new book from sociologist Terry Williams details the lives of people who lived in tunnels underneath New York City.

Williams has studied the city and its subcultures for more than 40 years, publishing books on subjects including street hustlers, after-hours clubs and building superintendents in Harlem.

To research “Life Underground: Encounters with People Below the Streets of New York,” he made hundreds of visits to the residents of “tunnels, hidden passageways, abandoned railroads, shelters and dungeons” across the city, from 1991 through 2020.

He said that people still live underground in New York City, though their population has shrunk in the ensuing years.

Williams said he began by studying three people living underneath Manhattan's Grand Central Terminal.

“My graduate students and I were sitting in the information booth there, and at around 12 midnight, people started to disappear,” said Williams, who is now a professor at the New School. “I started to follow people to see where they were going, and they were actually going five levels underneath Grand Central Terminal."

But he soon learned of a much larger community of more than 100 people living in an abandoned railway tunnel on the Upper West Side that was created when Robert Moses built Riverside Park in the 1930s.

Williams conducted his fieldwork between midnight and 6 a.m., approaching 120 underground residents for potential fieldwork and ultimately following eight, whose stories comprise the bulk of “Life Underground.”

Besides conducting his own interviews, he also gave residents tape recorders and journals to record their own experiences. He came to see the underground as a metaphor for the way we close our minds to unpleasant realities, including poverty, homelessness and mental illness.

“I wanted to know who they were,” Williams said. “I wanted to know what brought them to this particular place in their life.”

The book is dedicated to former tunnel inhabitant Bernard Isaac, who he said died in 2017.

Other tunnel residents deeply respected Isaac, whom they called the "Lord of the Tunnel," according to Williams, who followed him for decades.

“He was an extraordinarily brilliant man,” he said.

Isaac and a few others would collect books from the trash, the streets and sometimes directly from superintendents in apartment buildings along Riverside Drive. They would mostly sell the books to sidewalk booksellers on the Upper West Side.

“I always saw this as an example of the working poor,” Williams said, adding there was a “hierarchy” among the people he met living underground.

In 2012, Bernard Isaac joined Williams (pictured, left) at Princeton to discuss the underground in a talk

Isaac sat atop a “hierarchy of misery” underground, according to Williams.

“The low end of that hierarchy includes people who are in mentally challenged situations,” Williams said. “The high end are people who were selling books.”

Williams said media coverage of so-called “mole people” focused on sensationalizing their unusual lifestyles rather than trying to understand them.

He sought to combat that portrayal through his more than 20-year friendship with Isaac, including when Isaac moved into his apartment after Amtrak began clearing the tunnel out and readying it for resumed service in the 1990s.

“I wanted to tell the longest story possible about people; not about what happened to them so much in the short run, but what happened to them in the long run,” Williams said.