Athletes have been running the mostly uphill route from this village to Athens for about 2,500 years, ever since a swift soldier named Phidippides legged the 26.2 miles to deliver news of a military victory over the Persians. But with just three months to go until the Olympic Games return to Greece, the ancient path is hardly fit for the world's best modern-day marathoners.

Hundreds of dump trucks, excavators, cement mixers and laborers with old-fashioned pickaxes are working double shifts to widen the racecourse along a narrow highway, but are far behind schedule. About half the route remains under construction. In Marathon, the starting line is nowhere to be seen; even the local work crews say they aren't sure where it's supposed to go.

The asphalt ribbon is one of numerous venues that are still unfinished as Athens scrambles to prepare for the Aug. 13-29 Olympics. The Olympic Stadium -- site of the Opening Ceremonies and the track and field events -- needs seats, not to mention an 18,000-ton roof that began sliding into place only this week. Across the region, the sound of jackhammers echoes with the building of new roads, subways and sidewalks. Everything is dusty.

With so much undone, it came as a huge relief to the host city Wednesday when visitors from the International Olympic Committee wrapped up a three-day final inspection tour and pronounced themselves confident that everything would be ready on time. Denis Oswald, the IOC's chief overseer for the Athens Games, said he was impressed with the progress and credited the Greeks for picking up the pace. "I can really witness the progress," he said.

"In the past we had doubts," Oswald acknowledged at a news conference. "I am very happy to report all these doubts have disappeared. . . . No single project is at risk and we know everything will be delivered on time."

In 2000, the IOC threatened to take the Olympics from Athens because the Greeks, plagued by political bickering and government spending controls, had failed to show much headway since being awarded the Games three years earlier.

Since then, Greece has labored to prove that a small country -- population 11 million -- can successfully put on a $6.5 billion athletic spectacle. Complicating matters have been escalating demands for better security measures after the Sept. 11 attacks in the United States, followed by bombings in Istanbul last November and in Madrid two months ago.

"In 2000, we began meeting under the shadow of a yellow card and, since then, we have done seven years' work in just four years' time," Gianna Angelopoulos-Daskalaki, president of the Athens 2004 organizing committee, said after the IOC finished its tour Wednesday. "This is a fact and it's proof of what we Greeks can do when we work in a focused and professional way. . . . When the world's best athletes come to Greece for the historic homecoming of the Olympic Games, we will be ready to welcome them."

There are still plenty of obstacles. Athens officials tout the planned 75,000-seat stadium, with its bowlegged glass-and-steel roof, as the architectural centerpiece of this year's Olympics. But where Sydney completed its Olympic Stadium 18 months prior to the start of the 2000 Games, Greece waited until last year to finalize the construction contracts.

After repeated delays, there was some talk of pulling the plug on the roof altogether for fear that the enduring image of the Opening Ceremonies would be of a half-finished edifice. Similar concerns had already prompted a decision to scrap plans for a covered aquatic center and leave it as an open-air swimming area instead. But under pressure from the IOC, contractors began slowly raising the stadium roof with cranes on Monday and pledged to cap it off by the end of the month.

Landscaping provides another challenge. Because of all the construction activity, the land around the main athletic complex is a dust bowl that a single heavy rain could turn into a quagmire of mud. Officials promise tens of thousands of trees, shrubs and other plants, but not until July -- the hottest month of the year in Athens, hardly a conducive time for vegetation.

Traffic congestion throughout Athens, a ringing headache in normal times, has peaked because the Greek government is building so many new roads and transit lines to accommodate the expected crowds for the Olympics.

Many Athenians say they are willing to put up with the inconvenience because they figure the improvements will pay off in the long term. And despite the ticking clock and all the planning problems, they say they are confident that the transportation network will be ready.

Panayotis Lezilis, 38, is helping to build a four-lane expressway that will connect the athletes' Olympic Village with the stadium complex on the other side of town. He said the road was first delayed when workers unearthed archaeological ruins along the planned route, and then delayed again when one of the contractors went bankrupt.

"The government has had to pay four times what things should cost because of all the delays, delays, delays," he said with a shrug. "The electricity [for the street lights] is not ready yet. We need to put up traffic signs and we still have to plant some plants. But we will be ready. No worries."

Subway extensions, a new tram connecting downtown Athens to the seacoast and a suburban rail link from the airport are also works in progress. But government officials promise that they will be completed as well.

"If you came six months ago, you probably would have thought these things would never have been finished on time," Spyros Capyros, the Greek government's general secretary for the Athens Games, said in an interview "But right now, there is no risk whatsoever that the facilities won't be completed. Most of the remaining work is cosmetic."

Such promises will be sorely tested by the project to rebuild the marathon route. Although the Greeks have held races along the course for years -- it ends at the old marble Panathinaiko Stadium near the Acropolis -- officials decided to rip up most of the pavement because it was prone to flooding and included little space for roadside spectators.

Like many other projects, construction was delayed by lawsuits and financial problems with contractors.

The pace has picked up since March, when Greeks elected a new government, which pledged to redouble efforts to get ready for the Olympics. Government ministers now visit the route almost daily to urge on the work crews, according to local residents.

Opinion is divided on whether the deadline will be met. "It will definitely be done on time," said Nikos Stamos, 85, a native of Marathon, who keeps an eye on the construction from an outdoor cafe and store in the village.

His 75-year-old friend, Evangelos Katipis, wasn't quite as optimistic. "That's for them to know," he said, nodding toward the workers. "But it's definitely progressing very fast. You can see it every day."

The stadium roof in Athens began its slide into position on Monday after long delays. "We have done seven years' work in just four years' time," Gianna Angelopoulos-Daskalaki, president of the 2004 organizing committee, said.