Joseph T. Flakne, who turns 90 today, calls Mason Neck in southeastern Fairfax County "God's outdoor cathedral."

It's easy to understand why. From outside his log cabin, Flakne can see the Potomac River, with the Maryland shore to the east and Mount Vernon to the north. Fall didn't skip Mason Neck this year; the trees were a spectacular blend of gold, orange and maroon.

And animals -- deer, raccoons, beavers -- frequent the area. Mason Neck is the kind of place where people talk about seeing bald eagles from their back yards. Or, when the first swans return in March, telephone calls go up and down the river, "The swans are back."

Birds probably outnumber the 1,700 residents who live on Mason Neck's 14 square miles. Jutting out in the Potomac south of Fort Belvoir and east of the Lorton Reformatory, the Mason Neck peninsula begins east of Route 1 and stops at the river. The mailing address is Lorton.

"The Neck," as some residents call it, includes more than 5,000 acres of parkland divided among a wildlife refuge, state park and regional park at Pohick Bay. It also contains Gunston Hall, the colonial plantation home of George Mason, author of the Virginia Declaration of Rights, the forerunner of the Bill of Rights.

Though located in the Washington area's most populous county, Mason Neck has remained essentially unchanged since some of the first homes were built in the 1920s as summer retreats and hunting lodges for Washingtonians.

"It almost seemed like a place development skipped over," said Gary D. Knipling, who moved to Mason Neck from Lake Ridge about 10 years ago.

But Mason Neck has had to fight to remain an enclave of 682 single-family homes in a county where the pressure to develop land is strong, especially along the waterfront.

Beginning in 1965, when a developer proposed building a community of 20,000 people on Mason Neck, there have been at least 23 attempts to alter the use of the land there in a way that many residents opposed. The battles have solidified Mason Neck's five neighborhoods, making them more determined to resist future development.

"Mason Neck is the environmental jewel of Fairfax County," said Paul T. Haluza Jr., president of the citizens association. "The county is going to have to make a decision: to preserve the heritage of Mason Neck ... or allow it to be developed. I hope elected officials will carry on that tradition of preserving it."

Haluza, who moved to Mason Neck about 20 years ago from a Manhattan apartment, is typical of many residents of the peninsula who sought a refuge from city life.

"When I cross Old Colchester Road and Gunston Road {Route 600}, I feel like I'm crossing into another world," said Haluza, a lobbyist who commutes 28 miles each way into the District. "I'm leaving the hustle-bustle, high pressure world into a more relaxing, tranquil environment that is close to nature."

And water. Many residents sought out a place on Mason Neck that is near the Potomac. People on Mason Neck stare a lot at the river, as if it were a form of therapy.

Robert C. Newcomb, a retired Navy captain who moved to the Gunston Manor neighborhood in 1973, said that living on the river allows "me to put my mind in neutral."

"It is very peaceful and there's such a feeling of openness," Newcomb said as he scanned the river from his deck. Tugboats, barges and fishing vessels went past and a couple of mallards were scooting across the water.

Next door to Newcomb, a few hours later, Lorraine D. Buglia was sitting on her back porch looking at the Potomac. That's her special sanctuary, she said, "the place where I go with a cup of coffee to regroup."

"They'll have to carry me out of here," said Buglia, a former Gunston Elementary School principal and Lorton native who has lived at Mason Neck for 40 years.

Gunston Manor, where Buglia and Newcomb live, probably is Mason Neck's most diverse neighborhood. Much of it was built in the late 1920s when a developer believed there would be a market for a resort community of Cape Cod cottages and campsites on 25-by-100-foot lots. Flakne's log cabin was the sales office.

The Depression largely scuttled that project, and the houses that were built were occupied by poor families into the 1950s. New families came in and added on to the cottages or built new, bigger homes. Today, Gunston Manor's residents are a blend of middle- to upper-income families. Mason Neck's median household income is $46,000 annually, compared with the county median of $55,100.

"Some people might turn their nose up at a place like this," Newcomb said. "But we have a mixture of people of all incomes. They're all good ol' folks."

Newcomb, a real estate agent, said the lowest price listed for a home on Mason Neck is $150,000 in Gunston Manor, while the highest price is $1.5 million for a home on Harley Road, a secluded, inland neighborhood with five-acre lots.

Like the rest of the region, Mason Neck is in an economic slump, meaning that some homes have remained on the market for several months and sellers are lowering their asking prices.

Five years ago, home sales were relatively brisk, a result the strong regional real estate market and the fact that people continued to "discover" Mason Neck, especially members of the baby-boom generation who flocked to waterfront homes in Gunston Manor and nearby Hallowing Point, a half-square-mile neighborhood of about 150 custom homes.

"One of my clients went to Gunston Hall, saw my open house sign and bought a home that day," saidHarriet Crampton, a real estate agent who has lived on Mason Neck for 27 years. "They didn't realize this place existed."

For all its advantages, Mason Neck has some drawbacks. You can't get there easily; Mason Neck commuters typically use clogged Interstate 95 and Route 1, making travel times some of the region's longest. Some people don't like being cut off from civilization; the nearest convenience store and gas station is about seven miles away.

Animals traipsing through the yard and garden isn't always a plus, like when they bite off roses and nibble at the vegetables.

The real problem, for many people at least, is the lack of adequate sewage treatment. Many of the homes, especially in the Gunston Heights and Wiley neighborhoods, went from outhouses to septic tanks, but many of those systems are failing because the water table is high and the clay soil doesn't drain well. This leads to health concerns, not to mention worry about property values.

One alternative -- hooking up to the county's sewer line -- could cost about $3,000 for each home, but many residents fear that the price of bringing in lines would eventually be higher.

"The sewer would be an open invitation to developers to open up the rest of the neck for development," said Elizabeth Hartwell, leader of Mason Neck's preservationists for more than 25 years.

Other residents said there may be no alternative to hooking up to the sewer. The Fairfax Board of Supervisors this week took the first step toward resolving the conflict by launching an engineering study to determine the best technology for removing sewage in the two neighborhoods.

Flakne, a former Interior Department official, believes that bringing in the sewer line -- and development -- could be a mistake.

"We've overlooked the fact there's a limit to these God-given resources," he said, surveying the "cathedral."

"Mason Neck is one place we can demonstrate to the world that right here near the nation's capital we can live nicely and preserve what we have," he said.