His home is a concrete chamber about 14 feet long, 5 feet wide, with a ceiling barely taller than he is.

He is fastidious about maintaining order within his universe.

His plaid flannel shirt, a brown coat, an assortment of socks and underwear are suspended from hangers that are evenly spaced along a pipe overhead.

He keeps his comb on top of a metal door frame, always in the same spot. He tucks several pencils and a few pieces of paper in a cranny between a pipe and the low ceiling.

He stows plastic jugs of water at the end of the chamber, beside a neat stack of blue paper coffee cups from Greek diners. The top cup holds his toothbrush.

His bed is a pile of blankets on the concrete floor that he keeps swept clean.

The place that Bass calls home is little more than an urban mine shaft, an alcove tucked at the bottom of a subway emergency exit that zigzags up three flights of stairs from the tracks to the Earth's surface.

He jams the small metal door at the top to keep out intruders from above. But if there is danger atop his tidy little world, there is bedlam in the tunnel outside his alcove.

Manhattan's subway tunnels are a nether world with a population larger than many small towns. They are home to more than 1,000 people, almost all of them mentally ill, alcoholic or addicted to drugs. Initially, they slept on station benches or in subway cars. But eventually they burrowed into the seclusion of the tunnels.

It is a revolting world of trash, rats and mounds of feces. The air in the tunnel is dank and odorless, kept moving by 800,000-pound trains roaring by at 40 miles per hour. But there are alcoves where the odor of urine acts like an invisible blanket of ammonia.

The area is littered with the remnants of addiction - crack vials, broken crack pipes, empty wine bottles and bent hypodermic needles.

And there is darkness broken only by an occasional light on the wall. Few of the homeless own flashlights - they're too valuable - so they navigate mostly by instinct and memory.

Just beyond the end of the station platform, people sleep under layers of soiled blankets, on ledges an arm's length from the deafening trains.

There are spots in the tunnel that leave no clearance between a passing train, rails that carry 600 volts of direct current and the concrete walls.

Fifty-two homeless people died in the subways last year.

"It's a very unhealthy way to live, but I can't find a way elsewhere," said Bass, 43, who grew up in East Harlem. He has tried living in welfare hotels and homeless shelters, but he couldn't cope with the thieves and drug addicts who lived there.

But the tunnels are safe from intruders. Even homeless advocates don't bother to go underground, for fear that the place is too dangerous and tunnel dwellers are too "service resistant."

They want to be left alone.

The tunnel where Bass lives bores beneath a Lower East Side neighborhood that is a historical mecca for the destitute. The Bowery missions are only a few blocks away.

Bass, like many of the tunnel dwellers, spends his days "working" above ground, gathering food, clothing and money. Some sell books and clothing spread on the sidewalk. Others wash the windshields of cars stopped at traffic lights.

When the sun goes down, they head to the Second Avenue subway station, the foyer to about a mile of Depression-era tunnels that were built to include vast, empty caverns for an expansion that never took place. The space almost seems to have been designed with the homeless in mind.

Even before one enters the tunnels, the Second Avenue station is a surreal place. A silent man with owlish eyes wearing several overcoats stands on the platform night after night beside three pieces of luggage. He never seems to sleep. He never goes into the tunnels.

To get to his alcove, Bass descends a few stairs at the end of the platform and walks through the dimly lit tunnel for two blocks until he is underneath Houston Street.

Most of the tunnel people are not as tidy as Bass. Some sleep on filthy mattresses they have dragged down the tracks. Most have constructed beds of flattened cardboard and rags. They sleep amid heaps of newspaper and empty food containers.

Others have taken care to personalize their areas with found items. A Smithsonian magazine sits open beside one man's bed, where he rigged a light bulb from an overhead electrical line as a reading lamp. One man has placed a wicker night stand by his bed, upon which he keeps a butane lighter, a bottle of steak sauce, a bottle of skin lotion and a National Geographic magazine from 1976.

Here and there lie a few discarded stolen goods - a pair of white ski boots, a few boxes of used clothing. The contents of a purse - cosmetics, receipts, checkbook deposit slips with a suburban address - are scattered by the tracks.

Some of the inhabitants appear disoriented, teetering as they walk between concrete pillars, talking to themselves. One man crouches behind a three-foot-high electrical signal box, circling behind the shield to hide from a stranger passing by.

A man who is wearing sunglasses even though it is practically dark squats at the end of a secluded tunnel over a fire he has built. He is mumbling and cursing and is surrounded by gray smoke and eerie light.

The man is cooking fresh chicken by wrapping it in newspaper and setting it on fire. His sleeping area is covered with ashes; he seems oblivious.

The tunnel floors are covered with a fine, black dust - some of it ash, some of it the dust from subway brake linings. People who sleep in the tunnels have a distinctive, dark sheen to their clothes.

So it was with Sharon, 29, whose floral tights and bulky coat were smudged and stained as she bent over to gather her belongings into a shopping bag.

Sharon said she "works the street" as a prostitute to pay for her heroin habit. Women are rare in the tunnels, but Sharon said that several men who sleep in her area protect her, including the man who is the father of her fourth child. All of her children live in foster homes.

She said that conditions in the subway tunnel were uncomfortable and unclean. "But it's free, you know."

In the last two years, the Transit Authority has attempted to make life more uncomfortable for the tunnel dwellers by sending teams of police and maintenance crews through periodically to clean out the homeless and their possessions.

Lt. John Romero, the commander of the police department's homeless outreach unit, said the population in the tunnel near the Second Avenue station had dropped from more than 100 people who lived there two years ago. Maintenance crews, which once picked up 420 discarded syringes around the station in a single night, are finding less trash.

But it was clear the other night as Romero led a crew through the tunnels that the remaining underground residents are stubborn. Mounds of fresh trash and bedding had accumulated in the seven days since the last cleanup crews had passed through.

"What's your name, sir?" Romero said to a groggy man named David who was sleeping beside a fishing rod he kept for protection.

"We got a bus upstairs with food and shelter, everything. You want to give it a shot?"

Most of the men were compliant as they got up and gathered their gear. But only a few accepted Romero's offer for a ride to the shelter. Most were escorted to the street, where they trudged off into the night.

"They know we're going to come back, but we have to give them respect and leave for a while," said Herbie Carter, 35, who lay in a bedroll in a wedge-shaped space where two tracks joined together.

The police wake-up calls have become a routine for Bass, who is known as one of the most persistent tunnel residents.

"Gary, I know you're up there, turn on the light," Romero shouted from the track as he stood outside the emergency exit where Bass lives. A moment later, the light blinked on.

"They got something against me or something," Bass said as Romero and several other officers entered his room and ordered him out.

"It's cold out," Bass said. "The man come around every night hassling me. I'm trying to avoid going to an overcrowded crackhead place, crackhead shelter."

"We brought a medical team down here to assess him," Romero said. "They said he's schizophrenic but nonviolent. So he wouldn't be admitted to a hospital. He's not a drug user. And he's always coherent when we speak to him. He has been arrested a couple of times for trespassing, but arresting him serves no purpose."

Bass gathered his belongings and the police walked him up the stairs. They unblocked the door in the sidewalk and Bass exited onto Houston Street.

With the tunnels cleared of homeless, maintenance workers began moving through the tunnels to collect the trash left behind.

The workers dressed as though they were removing asbestos. They wore disposable moonsuits, dust masks and thick rubber gloves. Several carried backpack spray tanks to disinfect the trash with bleach before the workers touch it. Several workers carry tweezers to collect the syringes.

The Transit Authority estimated it spent $1.7 million last year just to clean up after the homeless.

"You take their bed - a couple of cardboards, a pillow, some rags - and a little food," said Reggie Adams, one of the cleanup crew, who said they did not relish confronting the tunnel dwellers. "It's like coming into your house and taking your watch and jewelry, that's how they feel about it."

As the maintenance crews worked their way through the tunnel, the homeless men whom the police had removed earlier began to drift back to the Second Avenue subway station. They sat on the benches with their blankets rolled under their arms, waiting for the crews to finish.

But Gary Bass did not bother to wait. Two hours after the police kicked him out of his lair, he had returned and lay sleeping once again beneath his blankets, his clothes neatly suspended above him on hangers.