A mural in Beijing's Underground City

A mural in Beijing's Underground City is dedicated to the workers who dug the labyrinthine tunnels, begun in 1969 as a mass shelter in case of war with the Soviet Union. (BRYAN CHAN / Los Angeles Times)

In 1969, China's leaders faced a problem familiar to Cold War veterans: How could they shield urban populations from military attack?

War with the Soviet Union seemed imminent. There had been skirmishes along the Siberian border. Diplomatic talks were deadlocked; nuclear weapons stood ready to be launched.

During the Cultural Revolution from 1966 to 1976, China's Communist leaders sent the nation's youth to the countryside to safeguard their proletarian minds from bourgeois thought. And Chairman Mao had a plan to protect proletarian bodies from Soviet bombs: Start digging, he said.

In the capital, 70,000 conscripted "volunteers" dug for a decade, creating a sinuous and unmeasured network of tunnels dubbed the "underground Great Wall." Like the Great Wall, it has become a tourist attraction.

But a visit to the Underground City reveals more than what is below the capital's bustling streets. It also showcases China's history, which endures in the traditional alleyways that are being turned to rubble for the 2008 Olympics.

In 1997, after a Peace Corps stint teaching college in the Chinese countryside, I moved to Beijing to teach and write. Graduate school at UC Berkeley tore me away, but last summer I returned to visit my former students.

When they said they wanted to see something especially and ephemerally Beijing, I got to thinking. Like most residents of the capital, I had heard rumors of secret passageways beneath its sidewalks. Soldiers were said to have entered Tiananmen Square from the tunnels during the 1989 crackdown on demonstrating students.

The capital was in the throes of another massive renovation. Its old gray brick walls bore slogans reading either "New Beijing, Great Olympics" or chai--knock down, raze. What should we visit before it was renovated into oblivion?

My old neighborhood of Haidian, in the northwest university district, wasn't merely unrecognizable since I had visited the year before; it was gone. And with it went ancient winding alleys, rows of spindly locust trees, duck and dumpling restaurants, sidewalk sweet potato vendors and grannies rolling their Rs as they chatted. In their place stood a new ring road, high-rise apartments and reminders of America: a McDonald's, Domino's Pizza and Starbucks.

At Haidian Book City, the emporium serving the student population, the best-selling titles reflected the city's balancing act between its insulated past and its future as a new member of the World Trade Organization. Alongside commentaries on modernizing the capital were new guidebooks showcasing its ancient streets and way of life.

I chose two, "Old Beijing" and "A Guidebook to Alleys in Beijing," which concentrate on the Qianmen neighborhood, where the entrance to the tunnels is. It is a working-class district cluttered with beauty salons, markets, newsstands and dozens of restaurants, sandwiched between the Forbidden City and the Temple of Heaven on the southern edge of Tiananmen Square. Qianmen, a warren of hutongs, narrow alleys that front four-sided homes, has remained physically unchanged for eight centuries. But modernization has begun to nibble at its edges, and, thanks to the Olympic make-over, soon it will be altered forever.

The next day four of my students met me at the two-story Kentucky Fried Chicken at Qianmen's edge, the area's most visible landmark aside from Chairman Mao's blocky, hulking sarcophagus. The kids, macabre as teens can be, wanted to see Mao's preserved body once more. We had gone twice last summer, so I urged them to consider the thick lines of people curving through Tiananmen Square under the searing sun. They relented at last.

We crossed Qianmen Avenue and stood at the head of Damochang Alley. It's only a short, dusty distance down the alley to the entrance to the Underground City, but the walk filled our morning.

The deep crimson of the Forbidden City's walls and the square's creamy vermilion monuments gave way to gray brick homes with grass sprouting from their tiled roofs. They are among the few hutong homes in Beijing that aren't preserved as living museums. We wound our way past two women swatting a badminton birdie, a woman shopping in silk pajamas and slippers, and a grandmother walking backward, urging her infant grandson to walk toward her. He was naked except for a red bib and tiny Nikes, and a small crowd had gathered to cheer him on.

One student asked me if scenes like this happened in America.

"I hope so," I replied.

I wasn't surprised when people began inviting us to take photos.

"This will all be torn down," one resident said. "We're not sure when, in the next couple of years maybe. We'll be moved to new apartments outside the Fourth Ring Road."

Her neighbor laughed. "Then we'll have our own bathrooms!"