Connoisseurs had described it as the most beautiful house in America and compared it to the most exquisite chateaux of 18th-century France. But the Chateau du Triomphe was a monument to modern American wealth and tastes, a $44.9 million estate whose main residence alone encompassed 43,000 square feet.

Overnight, however, that residence was gutted and charred by a fire of unknown origin that grew to six alarms. Parts of the mansion, nearing completion and occupancy after years of construction, were reduced to rubble.

For nearly eight hours, 100 firefighters fought to stop flames from consuming first one wing and then another, but the mansion's epic scale -- it's almost a football field long -- worked against it.

The house was built in the French Renaissance style, but it spoke to American excess: The 43,000 square feet of the main house made it more than 10 times the size of the home owned by the average upwardly mobile Dallas resident. Add to that the servants' quarters, 16-car garage and three guest living areas, and the dimensions surpassed 70,000 square feet strewn across 10 acres.

The master bedroom alone was 1,794 square feet.

Although the mansion was equipped with a fire-suppression sprinkler system, the apparent lack of firewalls in the attic allowed the fire to gallop almost at will, according to fire officials. They said they were unsure whether the sprinkler system was working yet, given that the house was weeks from completion.

"This was a big operation, and frustrating. We tried to head it off in the attic, but it just kept traveling and traveling," said Lt. Doug Dickerson, a firefighter who said this was easily the largest house fire in Dallas history. Fire officials' preliminary estimate of the damage was $23 million.

The cause of the fire is under investigation. "We are looking at the blueprints and interviewing everybody, sorting through the debris. We are going into this open-minded," Dickerson said.

The mansion was at 10330 Strait Lane, in a neighborhood some people call Billionaire Row. Former presidential candidate and EDS founder H. Ross Perot is a Strait Lane resident. So is Philip Romano, an internationally known restaurateur and art collector. The smallest residences weigh in at around 10,000 square feet, and servants' quarters, private lakes and sprawling grounds are the norm. But the Chateau du Triomphe exceeded even those standards, with its 10 bathrooms, a basement that housed 64 air-conditioning units, and an Olympic-size indoor swimming pool.

"We're the poor neighbors, by comparison," said Norman Green, who seven years ago sold the Dallas Stars of the National Hockey League to current owner Tom Hicks for $84 million.

Construction was begun in 1995 by George and Dominique Perrin, who sold the project to Jean and Natalie Boulle, who had planned to live in it but then sold it to a holding company created in 1999 for the sole purpose of completing and selling the estate.

The holding firm, Texas Treasure Fields Inc., has shareholders in Monaco and Luxembourg, said Steve Malouf, attorney for the firm. While the estate carried a listing price of $44.9 million with Christie's auction house in New York, the actual replacement value of the house today is about $70 million, Malouf said.

Neighbors said Boulle, a shareholder in Texas Treasure Fields, still talked of moving into the estate with his family one day. "We would have been thrilled to have them as neighbors," said Green, who recalled dining with the Boulles in Monaco last year.

"I would compare that house to the glory days in France when they built these wonderful, very elegant chateaux," Green said from his estate in Canada, where he is on a three-month vacation. "It's a very, very sad thing. It's like losing an icon in the country. There are not many places that are dramatically beautiful as that was."

The blaze was a frightening highlight of the summer for Grant Garrett, 14, who lives several houses down Strait Lane. He and his two cousins watched it burn. "I can't believe it's gone. It's the biggest house I ever saw," Garrett said.

Robert Flagg, a cameraman for a Dallas TV station, said he taped the fire all night long. "I've been to a lot of fires and I've seen a lot of firemen in action, but this one was just too big for them," he said. " . . .It was just too big a fire and too big a house."

The $44.9 million Chateau du Triomphe, with a 16-vehicle garage, was under construction and near completion when fire broke out.Larry Bickerstaff is one of 100 firefighters called to fight the six-alarm blaze in one of Dallas's most expensive neighborhoods. Flames apparently spread through an attic.