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Express bus 916 glides up to a stop in China's Huairou District, north of Beijing. Another stop or two and we'll get off. But when the doors slide open a man jumps on board, fixes his gaze on us and begins yelling, "Mutianyu! Mutianyu!" while frantically indicating we should disembark. Now!

Ed grabs his pack and starts to rise, but I pull my husband back onto the seat. "Ignore him," I whisper. The man is clearly a "black taxi driver," one of the illegal operators we've been warned about. They prey on unsuspecting tourists, ripping them off with inflated fees.

Knowing he's lost this sale, the man hops onto the sidewalk and the bus rumbles back to life. Minutes later we disembark at the proper stop, climb into an official taxi and zip the final few miles to the Mutianyu section of the Great Wall of China.

From the day I learned about China's Great Wall as a schoolgirl, I longed to see it with my own eyes. Now, my dream is about to come true. The Great Wall was constructed over a 2,000-year period, from the third century B.C. to the 17th century A.D. Its purpose: to protect China from barbarian nomads and northern aggressors. More than a few groups of marauders managed to breach the 5,500-mile wall over the centuries, yet it remained a potent symbol of power and strength — more psychological barrier than actual.

Today, much of the Great Wall is crumbling. Yet impressive stretches remain. The Badaling section in eastern China, about 90 minutes northwest of Beijing, is the most visited. At 4.7 miles long, it was the first section of the wall to be refurbished and, in 1957, opened to the public. This is the section that President Richard Nixon toured during his historic 1972 visit.

The Jinshanling and Jiankou sections are famed for offering challenging hiking amid wild scenery.

Mutianyu is notable for its architecturally unique fortresses and watchtowers, plus its scenic setting in a lush forest of pine, cypress and hardwoods. More enticing to me is that Mutianyu features an alpine slide.

I'm not sure why the idea of rocketing down one of the seven wonders of the medieval world on an alpine slide appeals to me.

The slide is yin to the wall's yang, yin-yang being the Chinese philosophy of complementary forces comprising everything in life: female and male, dark and light, earth and heaven. The historically significant and dignified Mutianyu segment of the wall must somehow need the puerile alpine slide to temper its splendor.

Me? I must need to discover what yin-yang forces lie inside, urging me to pay homage to Mutianyu's impressive architecture, then say adieu from atop a kiddie slide.

A path of 4,000 steps

Our taxi driver drops us off and we head into the park. To access the Badaling section of the wall, you simply walk right onto it from ground level. Not so with Mutianyu, which towers 25 feet skyward from its mountaintop perch. Here you must take a cable car or gondola to the top, or hike up more than 4,000 steps. Since we'll be effortlessly sliding back down the wall in a few hours, we opt to walk.

As we slowly make our way up the path, I catch glimpses of the granite wall through the trees and shrubs. Disappointingly, its drab, brownish-gray stones don't look impressive, ancient or formidable. But when we finally reach an access gate and clamber on top, I'm overcome with awe.

The crenelated wall unspools in great flourishes to our left and right, following the spiny, undulating ridge of the mountaintop. It's at once massive, yet diminutive — surely a dismaying sight to invading forces, but also a mere pimple on the Earth if you've just traversed the sea of harsh, jagged mountains I see stretching out before us. Yin, yang.

I anticipated an easy amble along Mutianyu's 1.5 miles, but we're faced with a strenuous workout. For the wall's top is wildly uneven, composed of thousands of steps of drastically differing lengths, depths and pitches. One minute we're skipping along inch-tall risers, the next we're crawling up foot-tall steps. Occasionally the pavement slants crazily from one side of the wall to the other.

Time to slide

Mutianyu is typically less visited than Badaling, but today it's humming with life. About half the visitors are wandering around bug-eyed and slack-jawed, quietly fingering the wall's timeworn stones. The others are lighthearted and irreverent, picnicking in the guard towers and carving their names into the weathered granite. Two dozen runners jog past, followed by a man in a pink bunny suit. Moments later we're motioned aside by lederhosen-clad young men toting brass instruments.

Suddenly, I get it. This wall, this very great wall, is a living, breathing piece of Chinese history and culture, and of the world's shared humanity. It's been the site of conflicts, bloodshed and tears, yet remains a place of wonder and incredulity, happiness and glee. Like the black-market taxi drivers who daily square off against their law-abiding counterparts, the Great Wall — namely Mutianyu — embodies the yin-yang philosophy that all things in life are inseparable but contradictory opposites. Just like me.

I gently lay my hands on the wall, then climb onto a metal slide car and clatter down the mountainside.

Melanie Radzicki McManus lives near Madison, Wis. Her most recent book is "Thousand-Miler: Adventures Hiking the Ice Age Trail."