Aboard The Beijing-Lhasa Express, China ? China’s first train from Beijing to Tibet set out Saturday carrying business travelers and thrill-seekers on the world’s highest railway, which critics fear could devastate the Himalayan region’s unique Buddhist culture.

The $4.2 billion railway, an engineering marvel that crosses mountain passes up to 16,500 feet high, is part of government efforts to develop China’s poor west and bind restive ethnic areas to the booming east. Critics warn that it will bring a flood of Chinese migrants, diluting Tibet’s culture and threatening its fragile environment.

The mood was festive aboard the train from Beijing on the 48-hour, 2,500-mile journey to the Tibetan capital of Lhasa.

“I feel very proud,” said Guo Chaoying, a 40-year-old civil servant from Beijing who said he was going to Lhasa on business. “We Chinese built this rail line ourselves, and it’s a world first, the highest. It shows our ability in high technology.”

The specially designed train cars are equipped with double-paned windows to protect against high-altitude ultraviolet radiation. There are outlets for oxygen masks beside every seat, for passengers who need help coping with the thin air.

Guo was riding in the lowest-price car, which had only thinly padded seats and no bunks, but he said he didn’t worry about resting.

“I’m too excited anyway,” he said. “There’s going to be too much to see.”

A few cars down, Tan Ji, a 40-year-old electrical engineer from suburban Beijing, was unpacking his cameras in his luxury compartment, which had four beds and a television.

A Tibetan woman holds a prayer wheel as the first train on the Qinghai-Tibet Railway crosses a bridge near Lhasa, the capital of Tibet. China on Saturday opened the first train service to Tibet on the world's highest railway, a controversial engineering marvel meant to bind the restive Himalayan region to China.

Tan said he planned to spend 1 1/2 days sightseeing in Tibet, then fly home.

“I’m really just going for the experience because it’s a first,” Tan said.

The opening of the railway coincided with a major political anniversary: the 85th anniversary of the founding of the ruling Communist Party.

“This is a magnificent feat by the Chinese people, and also a miracle in world railway history,” President Hu Jintao said at a morning ceremony in the western city of Golmud to inaugurate service on the railway.

The first train on the line pulled out of Golmud carrying about 600 government officials and railway workers. Minutes later, a train left Lhasa for Golmud. A third train left the western city of Chengdu later in the day for Lhasa.

The train from Beijing pulled out of the Chinese capital Saturday night.

On Friday, three protesters from the United States, Canada and Britain were detained after unfurling a banner at Beijing’s main train station reading, “China’s Tibet Railway, Designed to Destroy.”

Others planned protests Saturday outside Chinese embassies abroad.

Tibetans sit on the first train to use the Qinghai-Tibet Railway, the world's highest, Saturday at Lhasa Railway Station in Tibet.

Chinese officials acknowledge that few Tibetans are employed by the railway but say that number should increase. The government also says it is taking precautions to protect the environment.

The official Xinhua News Agency lashed out at critics, calling them hypocrites who want Tibet to remain undeveloped and a “stereotyped cultural specimen for them to enjoy.”

“Why shouldn’t Tibet progress like the rest of the world?” the commentary said.

The 710-mile final stretch of the line linking Golmud with Lhasa crosses some of the world’s most forbidding terrain on the treeless Tibetan plateau.

Xinhua reported Saturday afternoon that the train from Lhasa had crossed the 16,737-foot Tanggula Pass, which the government calls the highest point on any railway in the world.

Passengers signed health declarations saying they understood the risks of traveling at such high altitude. They were required to declare that they didn’t suffer from heart disease or other ailments that might make them susceptible to altitude sickness.

Communist troops marched into Tibet in 1950. Beijing says the region has been Chinese territory for centuries. But Tibet was effectively independent for much of that time.