Hannelore Sperling rises early in her 12th-floor condo in Crystal City, takes the elevator to the ground floor and steps into a corridor. Behind a glass wall to her right are two indoor tennis courts, bathed in fluorescent light. She walks down a ramp under a vaulted glass skylight. It is the last glimpse of daylight she'll see until lunch.

Down, down, down she goes on another ramp into a football-field-long corridor with taupe walls and a white, stipply ceiling. The overhead lighting shimmers off the high-buff, brown floor. The air is scentless, the temperature moderate. The predominant sound is the shuffle of men's shoes and the clicking of women's heels.

Sperling walks past color photographs of Crystal City at play; many of them show models shopping, swimming, picnicking. She passes people she knows; they exchange greetings like passersby on a city street. Except that here, in this underground tunnel, Sperling feels completely safe. It's never grimy or loud. You could pad to work in your socks, if you wanted.

About five minutes and a quarter-mile after leaving her condo, Sperling arrives at the underground beauty salon she owns, across a nine-foot-wide corridor from a psychiatrist's office. Within minutes her half-dozen employees will arrive. Ten hours later, another workday will have ended and she'll take the same stroll home, just as she has for nine years. This time, when she passes under the vaulted skylight, it will be night.

"I hear people talking about being stressed out from driving. I'm never stressed out. I don't even need a raincoat," Sperling says. "Last year when we had the blizzard, it was no problem. You can survive for weeks and weeks without going out. In the summer when it's really hot, I can stay nice and cool inside.

"It's like you're living in Heaven."

Crystal City is wedged between National Airport and U.S. Route 1 in Arlington County. Dating from the early '60s, its older buildings are about to get a face lift and management is coping with the potential loss of big government tenants in an era of downsizing. But that isn't what makes it Washington's most uncommon suburb. This is a self-contained, concrete-and-glass collection of squat high-rises, 150 acres of dense-pack city woven together with broad one-way streets flecked with pedestrians during the lunch hour but nearly deserted most nights and weekends.

That's because Crystal City exists largely indoors.

Larry Gofney is the deputy commissioner of the U.S. Patent and Trademark Office, which occupies 16 Crystal City buildings and, along with the Navy, accounts for 35 percent of the office space here. Gofney rents a three-bedroom apartment across 23rd Street at Buchanan House, which is not connected to the underground tunnels. So he walks outdoors to get to work. A little.

"I'm only outside for less than 30 seconds," he says. "I never take a coat, and, when there are times I have to fly to another city, I walk out of my home, over to the office and then my driver drives me to the airport. Then I get on a plane and end up in a place like Chicago, and all of sudden I realize I should have taken a coat."

Each weekday morning, Gofney and his wife, BJ, get up at 4:15 and power-walk to the Pentagon City mall, do a lap around the outside and come back. On weekends, they walk along the Potomac bike path to Alexandria for breakfast. But they spend much of their time indoors -- his wife takes the Metro to Catholic University, where she's working on a PhD. They ride the Metro to Union Station for dinner. They ride the Metro to Friendship Heights or Pentagon City to shop.

"So we never have to go outside," he says, laughing. They would have preferred to rent in one of the Crystal City apartment buildings connected to the tunnels, but none of those would allow their cat.

Since the Charles E. Smith Cos. erected the first apartment building in 1963, Crystal City has been a large, slow-moving target for critics -- architectural, sociological, cultural, you name it. As it grew through the '70s and '80s to more than 50 buildings -- most built and leased by the Smith company -- an extensive underground system of tunnels was burrowed to connect the offices and apartment complexes and provide an all-weather shopping environment. It's been called -- fairly or unfairly -- a concrete city, a lunar base, a molehill, a Habitrail for humans rather than hamsters, and a series of soulless canyons.

On the 11-block, 20-minute walk from one end of the underground complex to the other, you'll pass more than 175 shops and restaurants. Fifty thousand people work here. There's a hardware store, a cobbler, a comic book shop and a grocery. A Japanese restaurant and a deli. A chiropractor and a nutritionist.

There is an oddness to the concept of subterranean human life, and it prompts the more fanciful to conjure up images of Strangelovian bomb shelters buried beneath an uninhabitable Earth's surface. Indeed, the design of Crystal City engenders a specific lifestyle -- one based on convenience, safety and filtered air. It is a design that promises -- and delivers -- a spit-and-polish rampart against life's many invasions, including the natural elements. Things are safe, orderly and well appointed. Which is why it's hard to find anyone who lives here to seriously bad-mouth Crystal City, except for the occasional joke about a human ant farm.

Charlie Brown uses his two-bedroom, seventh-floor Crystal Gateway condo as an ultra-convenient way to keep on top of his work. The former Vietnam helicopter pilot is a marketing executive for McDonnell Douglas. When he retires, he'd like to move to Florida where he can have a pool and play golf in the sunshine. But for now, he doesn't want to worry about the security of his apartment when he's sent on two-week business trips. And he's not the outdoors, house-fixer-up type, anyway.

"If I'm working on my computer and want to go out to eat, I'll walk though the underground to Hamburger Hamlet and have a sandwich and a couple beers and go back and never see the light of day. Sometimes, I've done that for a weekend or a three-day weekend," he says. Crystal City "is really good for a guy or a gal who wants to spend a little more time making sure they survive all the downsizings that are going on around the country, if they want to put in a little extra time and effort to assure that they're competitive or more than competitive."

This is a no-muss, no-fuss lifestyle -- no yard to mow, no roof to fix. It's ideal for people who have decided to throw themselves into their professions for a highly intense, usually brief period and who can't, or won't, spend their time on activities that cut into their work time. Accordingly, there are a number of young singles and older people, with few children among the 6,000 residents. In television's "The X-Files," FBI Assistant Director Skinner, the unmarried, childless boss of agents Scully and Muldar, logically lives in Crystal City.

Sen. John McCain (R-Ariz.) may epitomize the Washington work ethic. His 17th-floor, two-bedroom condo, which overlooks National Airport and the Mall, is "a place where I lie down and get up and leave" in between 18-hour workdays. He just met his neighbor recently -- after living next to him for four years. "Sometimes I've gone three weeks without going into my living room. You can start to feel more like a mole than a human."

When he's at his condo, the former Vietnam fighter pilot likes to stand on the balcony and watch jets take off and land at the airport. Crystal City, with its proximity to the Pentagon and its well-oiled, everything-in-order lifestyle, appeals to military folk or those associated with the defense industry.

"It's such a utilitarian existence," McCain agrees. "You don't have to spend your time or energy on living conditions."

Exactly, says Tom Moser, an aerospace engineer who worked on the Apollo program in Houston. He works for ANSER, a think tank that monitors the Russian space industry. He can walk to work through the tunnels or through an underground parking garage, or go outside if it's nice. For him, Crystal City is a can-do place.

"The living is easy. The lack of wear and tear physically and mentally is unbelievable," he says. "Also, Crystal City is really appealing aesthetically. On the weekends, there's nobody here. In the evenings, there's nobody here. It's as quiet as the suburbs."

He and his wife, Nelwyn, own a 100-acre ranch in the Hill Country of central Texas where they'll retire in a couple of years and breed longhorn cattle. How does a man with a ranch in wide-open Texas stand to live in a high-rise city?

"Well, that is a contrast, but the similarity is that we absolutely have to have a view wherever we live," he says, talking on the phone from his balcony. "Right now, I'm looking at the Washington Monument and the Capitol. That's as good a view as you can have in the world. At the ranch, I can look 30 miles away at the Guadalupe Valley and the hills and everything else.

"A few minutes ago my wife said, Yesterday was the first time I've been outside since Saturday,' " which was four days earlier. "When you have a fantastic view, you don't have to go outside." Interior Motives

There's a view just down the tunnel from Sperling's beauty shop. It's a bluish-purple sky arching over warm, salmon-colored colonnades. Large green shrubs bend in the breeze. It took Freya Grand three weeks to paint this view on the walls and ceiling of a previously white-walled corridor dogleg. It runs for about 12 feet along the walls and arcs across the low ceiling. At one end is a utility room door; at the other are twin ATMs.

"I don't think when they built {Crystal City} the idea was to deprive people of light and color, but that was the end result," Grand says. "This will inject brightness and humanity into this tunnellike space."

In a way, the mural is better than the real outdoors -- it can be viewed year-round with no fear of inclement weather. A wag would call this irony. Residents, however, would say the Smith company is again responding to their concerns.

"Years ago, the criticism of the Charles Smith company was that they're building a concrete city,' " Sperling says. "So they started to build parks and green spaces and the water park so we didn't feel so isolated."

Indeed, the lush landscaping between buildings is so well maintained, it appears the grass has been cut with fingernail clippers. The renovated southern end of the underground shopping center is skylit and airy and has none of the space station feel of the northern, older corridors. The bare-walled corridor from the underground shops to the Marriott Crystal Gateway, on the other hand -- one of the older legs of tunnel -- dips down and then up in such a fashion as to induce spatial disorientation.

But soon, every older section of Crystal City will be renovated, says Robert Smith, president of the Charles E. Smith Cos.

Inside his 11th-floor office overlooking the new National Airport terminal, Smith tells how his father, Charles E. Smith, tried in 1961 to talk his son out of building the first Crystal City apartment -- Crystal House -- because tenants would have to drive past a junkyard and other low-rent properties to get to it.

"Did you put money down?" the elder Smith asked. "Take the loss. This isn't us. We're Connecticut Avenue. We're downtown," he said, ticking off the family's successful rental properties.

But the 32-year-old son, determined to make it on his own, finished Crystal House on the west side of Route 1 two years later and soon filled it. He named it for an elegant crystal chandelier he bought in Miami that still hangs in the lobby of the 12-story, brown brick structure. "Crystal" became the first name of the city's buildings.

Four years later, he moved across then-two-lane Route 1 and built the Crystal Plaza office buildings. Needing a large tenant, he lured the General Services Administration for the bargain-basement price of $4.09 per square foot. Because the rent was so cheap, Smith couldn't spend much on architecture, which explains the buildings' Eastern bloc look. And, penned in by Route 1 and the airport, Smith could only go underground to provide parking and shopping; he patterned the underground shops after a complex he saw in Montreal.

Sometime in the '70s, Smith realized he had created a community, and needed to supply community amenities. He began landscaping with large trees. He built an ice-skating rink and a movie theater. Because no high-end restaurants would come in, he built his own. Later, he added a park with a waterfall and a bandstand for summer evening concerts.

"We were doing anything we could to soften the environment," he says. Also, as rents went up, he could afford to build better-looking buildings with soaring marble-and-glass lobbies.

Now he is considering updating the facades of the 30-year-old buildings and is concentrating on keeping the offices full as the Navy slowly pulls out and the Patent Office considers leaving. Smith is president of the National Gallery of Art -- his office walls are covered with 18th-century Venetian etchings -- but Crystal City is his lifelong passion.

He asks: "How many men get to start with a blank sheet of paper and create a city?"

Crystal City's secret, planners say, is that it works like an old town center, a fact hidden because so much is underground. Unlike a master-planned community built all at once -- based on avant-garde planners' often unrealistic theories about how people should live and work -- Crystal City was built piecemeal, which meant it could grow organically and respond to the needs of the residents. Where Rosslyn and its skywalks-of-the-future failed, an Arlington planner says, Crystal City has succeeded by combining residential and commercial uses and creating a community underneath the traffic.

"If you drive by Crystal City on Route 1, your reaction is Ughh,' " says Robert Brosnan, director of community planning, housing and development for Arlington County. "But if you drive down and walk into it, you'll find something different."

Much of the criticism, Brosnan says, was leveled at the utilitarian architecture of the '60s and '70s buildings and the fact that they vary little in height because of airport restrictions, creating a dull, uniform skyline. But the thing works, he says.

"You do both indoors and outdoors," Brosnan says. "When it's crummy out, you can take the elevators from the residences to the shopping core and go up the elevators to your office, but there certainly is enough stuff outside, like the water park, that really draw people out." Surfacing

On a recent late afternoon, a rainstorm blew through Crystal City, which you might not know had you been underground. But if you took the Metro escalator up to daylight, the smell was unmistakable: that cool, fresh scent of after-rain, carried on the light breeze that always trails in the wake of a spring shower. A whiff of juniper bushes followed. The sunshine warmed the face like a towel just out of the dryer. The traffic rushed and clattered overhead on Route 1. This was life outdoors -- sensuous, random, loud and untidy -- and the people coming up the escalator from the spotless underground drew breaths of it as they broke the surface of the planet. CAPTION: Tunnel traffic underground where residents may not see the light of day for days. CAPTION: Freya Grand painted tree-studded colonnades to bring the outside in. CAPTION: Above, Tom and Nelwyn Moser appreciate their piece of the skyline; below left, Hannelore Sperling, surrounded by stylists, at her subterranean Beauty Encounters; below right, Crystal City is 150 acres of squat high-rises and lush greens woven together with broad one-way streets.