Nearly 3,000 miles of sewers wind underneath Philadelphia's streets. They make modern life possible in the homes and sky-scrapers above, but go largely unnoticed.
Except, that is, by one man whose job it is to uncover what the city looked like before they were there.
Enter Adam Levine, a historical consultant for the Philadelphia Water Department.
Levine is so fascinated by the network of sewers transporting waste away from the city that he has been researching the underground maze part-time for more than a decade.
He got his job after taking a sewer tour and writing about it, so he agreed to accompany me on a tour of my own, which led us underneath Algard Street in the Northeast.
The brick sewer was tall enough to stand in comfortably, and about four inches of gray water rushed by our rubber boots. It was humid and sticky, and smelled only mildly of sewage.
Sewer maintenance inspector Kevin Bess took the lead on the tour.
He stopped during our block-long walk underground to point out a softball-sized opening in the wall of the sewer, at about eye level: the opening of what's called a lateral pipe.
"This is the last pipe that brings all the used water from your home," Bess said.
I asked what happened if that house flushed the toilet while we were looking at it.
"Move out the way," Bess replied. "Whatever they flushing, is coming down into the sewer."
Bess has been walking, and sometimes crawling, through Philadelphia's sewers for 16 years. So he doesn't tend to linger underground.
"You want to come down here, find out what's going on, and get out of here as soon as possible," Bess said.
A fascination with underground streams
Back on the surface, Algard Street is quiet. Levine, who had been down in the sewers only twice before, is already waiting on the sidewalk. His reaction afterward has been the same each time, he said.
"I come up and I look up at the closed man hole and I look at the street and I can't believe where I've just been," Levine said.
Levine said he partly likes going into the sewers because not many people can. Largely, he is fascinated by how what is there now compares to what used to be.
"This sewer was built in 1915 and before that there was a stream meandering more or less down Algard Street, there was a pond right up stream near Tyson Street," he said, referencing the hand-drawn historical map in his hands.
He points to a stream that used be where the street now is. It was routed underground to make a sewer, a common practice as Philadelphia was being built.
A similar underground stream first piqued his interest in the sewer system back in the 1980s. He had been working in a community garden in West Philadelphia when he was told that the houses that had once stood there had been undermined by an underground stream.
"I couldn't believe that a stream would have been put in a sewer," Levine said. "I couldn't comprehend that."
A child of the 1970s, Levine remembers celebrating the first Earth Day. He seems a bit wounded on behalf of those creeks.
"I couldn't figure out why anybody would want to do that to a stream," Levine said.
Wounded but fascinated
In 1997, Levine went into that West Philly sewer to write an article for City Paper. The water department liked it so much, they offered him a job as a part-time archivist.
Spokeswoman Joanne Dahme said the lectures Levine has given on what specific neighborhoods used to look like are especially popular.
"We have found that history is a fantastic hook," Dahme said.
It helps people understand, for example, why it matters that their house is on top of a former stream bed.
"People will say to us, "Oh, I have a better understanding about why my basement is wet all the time.'
The city seen through a different lens
Levine's research usually takes place high above the sewers, in his Center City office, where more than 20,000 reference documents sit in cardboard boxes, on book shelves and in filing cabinets.
Levine said after years spent looking at historical views of the city, walking around is a little different than it used to be. He's constantly on the lookout for slight depressions and elevations of the land. Evidence, he knows, of hilltops being shaved off. The dirt likely was carted away to fill in low-lying streams and valleys.
"What I see is I see the city as a whole series of cuts and fills and missing pieces," Levine said. "Anything natural was a problem in any city that has a grid of streets, because the grid doesn't bend and nature is not rectangular."
Now, Levine's work will help bring this man-made system a bit closer to nature.
His records will help Philadelphia place rain gardens and reservoirs in the right locations as part of a new green storm water management plan.
Back on the street in Northeast Philadelphia, Levine held on to the hardhat and Tyvek suit he wore underground. Souvenirs to take home.
"My friends things I'm a little weird anyway, and a little crazy," Levine said. "Why not just make them happy, and prove that they're right?"
Though Levine speaks wistfully of the days before man re-shaped the city, he clearly respects the engineering it took to create it in the sometimes swampy land between two rivers. Since he said he doesn't have much competition for his job, he will continue archiving and studying that engineering as long as someone keeps paying him.