BADALING, China — At Badaling, a popular destination outside Beijing, the Great Wall of China rides the ridge lines like a dragon, its gray brick scales glinting and its crenelated spine writhing. Built at a strategic pass in the mountains north of Beijing, it crosses stout gates, plunges into narrow defiles, climbs back up to the heights and seems to go on forever.

Long after this month's Olympic Games end, people will flock to Badaling, where seeing is believing in the Ten Thousand Li Long Wall of ancient annals and legend. But contrary to the impression it makes at Badaling, the Great Wall may never have crossed China in one mighty, continuous span, nor is its length precisely known. (Some say it's 4,500 miles, others a mere 3,100.) Experts now think of it as a series of disjointed segments built at different times in the last two millennia and scattered in a maze all over northern China.

Badaling is the centerpiece of an estimated 380 miles of Ming dynasty (1368-1644) fortifications in the capital region, the highest concentration of Great Wall in China. The site is about 43 miles from Beijing and easily accessible. It opened as a tourist attraction in 1957, with visitor facilities and well-maintained, relatively gradual steps to the top where visitors see long stretches of reconstructed brick and stone wall, together with a knot of spurs and cunningly engineered Ming watchtowers. About 4.5 million people visit each year.

Here's a spot review on Great Wall history:

Purpose: To protect against invaders from the north.

Claim to fame: Longest structure ever built; symbol of China's violent conquests and architectural acumen.

Construction start: 5th century B.C., though estimates vary.

Length: About 4,000 miles.

Base width: 15 to 40 feet.

Height: 20 to 50 feet.

Made of: Stone, brick and earth.

Named UNESCO site: 1987.

Sources: Encyclopedia Americana, World Book