Most of the time, the neighborhood is quiet.

That's one of the first surprises about Sun Valley. So many people living in such a small area, and yet it is so still. Sun Valley rouses itself, like other neighborhoods, for morning coffee and the walk to the bus stop or school. Then it settles again, as if gathering itself for the after-school, back-from-work, time-for- supper hubbub.

But something else runs through the quiet. It is not despair, though that makes appearances here. It is not resignation or exhaustion, which are frequent visitors. It is more the sense of a people who have come to believe themselves invisible.

"What do people say? We're the land of the forgotten," says Toni Cisneros, who raised her children and is now raising a nephew and taking care of her granddaughter in Sun Valley.

Sun Valley is a pocket of at least 1,300 people, nearly all of whom live in public housing. This is not just a poor neighborhood. It is, by far, the state's poorest. It is not just an isolated neighborhood. It is Denver's most isolated, hidden amid industry, walled off by river and road. It's the neighborhood you're not supposed to see, the product of accident and design, cynicism and idealism.

The combination of poverty and isolation has acted like slow poison, sapping human and economic potential. It has hurt the city and neighborhood residents, most of whom are children.

But an opportunity has arisen to change that. The West Corridor light-rail line from downtown's Union Station to Golden is under construction. In 2013, a light-rail station will open here, just east of Federal Boulevard about a half-mile south of Invesco Field. People in and out of the neighborhood have been planning the transformation of Sun Valley into a well-rounded community for those who live there now and those who will come.

No other neighborhood may be as hard to change.

West 13th Avenue is the only street that enters Sun Valley's residential section from downtown Denver. It takes you to a handful of houses, old and in various states of decrepitude. They sit at the tail end of an industrial stretch crisscrossed by trains and freeway lanes, a power plant and substation. Railroad crossing signs flash, and vapor from underground steam pipes drifts across the road. Women push strollers, and men wrestle grocery carts along dirt shoulders.

West 13th leads to Decatur Street, and Decatur cuts through the center of Sun Valley. Here, the housing projects come into view. They're not what you'd expect, if what you expect is forbidding, gray towers. Sun Valley is brick and stucco apartments, laid out in one and two stories along winding roads and around well-maintained common greens. A handful of new playgrounds are scattered among the buildings. Clotheslines sag with pants and shirts and blankets, drying in the sun, forgotten in the rain. The air carries the smell of detergent and bacon and frying potatoes.

Federal Boulevard lies a block west, up the hill, along the bluff lined by the towering Denver Department of Human Services building, the Westside Family Health Center and the Family Crisis Center. Thousands of people a day drive past Sun Valley and never know people live below.