When Neal Conroy walks down the street, he is always on the lookout for a hole to crawl into, a gateway to someplace that lets him disappear. On this chilly night in mid-November, that gateway is a sleepy intersection in Irving Park. It doesn’t look like much: a raised traffic circle surrounded by a few manholes. But when he reaches the spot, guided by an old Metropolitan Water Reclamation District map, Conroy says in a hushed voice, “This is the one,” as if he’s reached Elysium. The street’s features, he says, suggest something big beneath: the type of wide horizontal tunnel that drainers — as urban explorers of his ilk are called — seek out.

He slaps on a pair of blue latex gloves and kneels in front of a steaming manhole. Conroy has a slender build, close-cropped hair, and, at age 30, the patchy mustache of a try-hard teenager. He swivels his head, scanning his surroundings. The hum of traffic on a nearby arterial street is the only sound. Coast clear, he pries off the 120-pound cast-iron cover with a grunt and shines a flashlight downward. Vapor pours from the opening like it’s a witch’s cauldron, obscuring the view. Rushing water — runoff from melting snow, Conroy says — can be heard. Then, without further ado, he slips like a spooked rabbit down the rusty iron ladder and vanishes from sight.

Conroy’s life began heading down the drain, so to speak, one Saturday morning in the mid-1990s, when, as a grade schooler, he first watched Teenage Mutant Ninja Turtles. He envied the wisecracking heroes in a half shell not so much for their martial arts prowess as for their spacious sewer lair, far from the city dwellers above who would label them freaks. Conroy could relate. He struggled to socialize at school, fixating instead on solitary interests. When he was in the fourth grade, he received a diagnosis of “pervasive developmental disorder not otherwise specified.” The condition, now classified as autism spectrum disorder, was typically also marked by hypersensitivity to sensory stimuli such as loud noises and lights. “I grew up thinking about having a big treehouse,” he says.  A place of inviolable solitude. But treehouses were hard to come by in Chicago, and before long, its sewer system, with 4,400 miles of tunnels and pipes, beckoned. “It’s like a treehouse, but underground.”

For a long time, Conroy was content to feed his fascination by snapping photos of manhole covers. Sometimes he would position the camera between the bars of a storm grate, using a flash to expose whatever lay in the darkness below — rainwater, moldering leaves, cigarette butts. But eventually he grew bored of the view from above. In 2008, at the age of 20, Conroy took his first plunge, shimmying into a tunnel under Lawrence Avenue near the river. “I didn’t have a powerful flashlight, so I didn’t go that far in,” he recalls. “I could see, like, a round brick tunnel. And I go, Man, I gotta come back again and go further. ”

And he did go further, down and down the rabbit hole of his peculiar preoccupation, supporting himself with a series of part-time jobs and sleeping in abandoned buildings for months at a time. (He’s currently living with his father in Rogers Park.) Conroy earned a bachelor’s in chemistry from Northeastern Illinois University in 2012; his capstone project was on sewage and water treatment. In the past 10 years, he has managed to explore a few dozen sewers across the city, usually in the wee hours, returning to the surface with photos and videos, which he posts on his website.

The site is populated with underlit shots of corroding drainage lines and Blair Witch Project–style footage of Conroy splashing through cavernous passageways illuminated by his headlamp. He has also created pages dedicated to his favorite sewers. Some get pet names: My Secret Dungeon, My Secret Chamber, My Secret Fortress. Others he identifies geographically, by the nearest street: 19th Tunnel, Western Tunnel, Franklin Lower Tunnel, Pershing Sidewalk Tunnel. He delights at encountering “waterfalls,” the Niagara-like cascades created when runoff from one sewer plunges into a deeper one.

A sewer tunnel photo
A photo Conroy took of a tunnel running under Ashland Avenue.

Before returning to the street, Conroy sometimes leaves a calling card: a small photograph, a self-portrait, taped to the tunnel’s interior. Some of his selfies show him in a suit and tie and holding a spray of flowers — a kind of public relations effort aimed at winning over any police officer who would seek to apprehend him. In the photos, he looks calm and contented in a way he doesn’t always appear aboveground. One caption reads: “Me at right where I belong.”

Of course, shit happens, quite literally, in the sewers. And yet Conroy’s protection, when he bothers to don any at all, consists of little more than plastic shopping bags fastened around his shoes. To the professionals who actually get paid to understand and maintain the city’s bowels, Conroy’s subterranean missions are a cause for alarm. Several years ago, in an uncanny twist of fate, Conroy rented an apartment in McKinley Park owned by a Metropolitan Water Reclamation District engineer. When Conroy would brag of his exploits, the engineer would sternly warn his young tenant of the perils of draining. The main concern, explains the engineer, who doesn’t want his name revealed, is a lack of oxygen from the buildup of toxic gases in a confined space: “If he passes out, he can drown, and no one knows he’s down there.” In Chicago’s sewer system, where storm runoff and sewage mix, there’s also the danger of being swept away by a sudden deluge, as was the case in the death of a 25-year-old maintenance worker who drowned in an Avondale sewer in 2013.

All this is to say nothing of the risk of contracting diseases like hepatitis or getting bitten by a rabid rodent. “I told Neal, ‘There are rats the size of dogs down there!’ ” the engineer says. Indeed, Conroy photographed a particularly plump Rattus norvegicus paddling through one sewer’s gray muck. He has traversed spillways teeming with earthworms and been startled by a cluster of crayfish that he initially believed to be scorpions.

So far Conroy has avoided major injury, though on his website he recounts a mishap in a tunnel made of slick precast concrete: “I slipped and fell again, landing on my butt. I got mud (or sewage) on the back of my shorts and the only things that got wet are my keys.” Minor scrapes aside, he has managed to emerge time and time again relatively unscathed — if not always unnoticed.

One night in 2010, Conroy dropped into a manhole near Joong Boo Market in Avondale. A police officer witnessed Conroy’s descent, and he looked into the sewer and asked what the young man was doing. According to the police report, Conroy answered simply, “I’m visiting.” He’d been stopped by cops twice before and let off with a warning, but this time he was charged with reckless conduct, a Class A misdemeanor. It didn’t help his case that he was in possession of a road flare (“for visibility,” he tells me), as well as a can of pepper spray and a bulletproof jacket (“for safety”). While in lockup at the 17th District police station, he overheard officers call him “Sewer Man” and “the Teenage Mutant Ninja Turtle.” A judge ordered Conroy to complete 50 hours of community service. After he’d logged his time, he sent his arresting officer a homemade greeting card. The cryptic note’s only text read, “Happy Valentine’s Day!” It was typed above a photo of an open manhole. The message was clear: Once a drainer, always a drainer.

On this night, emerging from the manhole in Irving Park, Conroy looks unhappy. It seems the tunnel is too narrow to navigate. He’ll have to check the other manholes nearby. As he’s about to slide the cover back in place, a middle-aged man moseys by on a late-night walk with his two dogs. Gazing at his phone, the man doesn’t seem to notice the stranger doubled over a hole in the road. The dogs, however, catch sight of him and begin straining at their leashes. Conroy stares back, still as a statue. The man, without taking his eyes off his phone, corrects the dogs with a yank of the leash and rounds the corner. Conroy exhales. Then he finishes inspecting the other manholes. After closing the cover of the last one, he announces that the only entry to the large sewer chamber is blocked by a locked gate.

The night’s mission would appear to be a bust, but Conroy, unfazed, mentions that he’s been itching to check out some other manholes in the area. Without so much as a parting word, he hurries up the street and disappears into the darkness.