Giuseppe Cecchi, the man who built Washington's Watergate, has picked a surprising site for his latest major project: the slightly seedy Rte. 1 corridor of southern Fairfax County.

"This is not a gamble," says Cecchi, who paid $3.1 million for an undeveloped 35-acre site on which to build four 15-story residential towers. "I feel very comfortable."

What makes Cecchi feel so good about the humble rte 1 strip, a hodge-podge of service stations, fast-food outlets, an adult bookstore and shabby trailer parks, is the bright orange steel viaduct now slicing into the county from nearby Alexandria.

The viaduct will carry trains -- the subway trains of Metro's Blue Line -- to and from Huntington Station, Fairfax's first Metro stop. Although the station's opening is two years away, Cecchi and others are confident its impact on this low-rent corridor will be extraordinary.

"It's a hot area," says Samuel A. Patterson, Fairfax's supervisor of assessments. "The Metro station has really stirred things up."

Already feeling the force of economic change are the Hunting Creek Club condominum apartments located along the Capital Beltway at the gateway to the Rte. 1 corridor -- an easy drive to downtown Washington for commuters shocked by rocketing gasoline prices.

"We could hardly give them away a few years ago," says B. J. Herzog, an agent at Mount Vernon Real Estate. "Now, the prices are unbelievable. An efficiency -- just an efficiency -- went for $26,000 last year. This year it's in the 30s."

In the long-deteriorating neighborhood of Huntington two-bedroom, red brick duplexes are shoehorned onto small lots.

"That's been a rough area," said Beth Haney, who sells for Gussie Real Estate in Alexandria. "I wouldn't go into the 7-Eleven after dark. But I look for big change. Those duplexes could be fixed up to look like Old Town."

Again change already has come, at least in the prices. In 1979, the duplexes were assessed by the county in the low and mid-thirties. Some recent selling prices: $58,000, $59,000, $61,000, $62,000.

Farther down Rte. 1. 35-acre Mount Eagle, which offers a 360-degree panoramic view of the Washington area, sat undeveloped for six years despite its high-rise zoning. Last year, Cecchi snapped it up for his four towers. The expected price range when completed: $58,680 to $116.955 per unit.

Over the years, business interests, citizens' groups and the county government all have tried to put together programs to upgrade the corridor. The efforts failed, and neighborhoods continued to decay. Cut-rate strip development (including bars and bookstores featuring "adult entertainment") spread down Rte. 1 and developers with prestige projects kept their distance.

Now, says Fairfax Supervisor Sandra L. Duckworth (D-Mount Vernon), whose district includes half the corridor, "things seem to be coming together. . . It will not be a false start this time. Too many good things are happening."

In addition to Metro, she points to federal housing rehabilitation funds in the form of low-interest loans that have poured into Huntington and another down-at-the-heels community, nearby Fairhaven.

The efforts of a corridor-wide committee of citizen business-government interests to upgrade Rte. 1 and attract classier establishments also has been a factor, she says.

Then, of course, there is Cecchi's Montebello, another condominium complex planned for construction. Not far up the road from the Dixie Pig Barbecue, a favorite stopover for interstate buses on Rte. , but its 1,200 apartment owners will live high on a heavily wooded hill.

"I don't think the real value of being next to a Metro station has been appreciated," says Cecchi, who says Montebello's residents will be able to get to the Huntington Avenue station via a three-minute shuttle ride.

After years of attracting few buyers, Huntington now attracts not one but two kinds -- those looking for a place to live and those looking for an investment.

James E. Cockrell recently bought half of a duplex at 2109 Arlington Ter. for his new home. Cockrell paid $48,000 for it, $14,120 more than its assessed value, but he is not complaining. "I got it for $6,000 less than what neighboring places were going for," he says.

Gerald M. Terlitsky bought 2024 Arlington Ter. for $43,000 last year. He plans to keep it as a long-erm investment, Already, he estimates, its value has increased by $8,000. "Isn't that something?" he asks.