The Great Wall of China is one of the most famous historical and architectural landmarks in the world. No other structure rivals the Great Wall of China in historical significance, size or grandeur. It dates back to the fifth century B.C., is more than 4,100 miles long and is China's most popular tourist attraction. There is simply nothing else like it on Earth.

Size
No man-made structure comes close to the size of the Great Wall of China. It runs 4,163 miles, or 6,700 km, across the People's Republic of China. It starts in the China Sea town of Shanhaiguan and stretches west to Gansu province roughly along the southern edge of Inner Mongolia. It crosses deserts, plains and rugged mountains. In some areas the Great Wall of China is 26 feet tall and 20 feet thick.

History
The Great Wall of China actually refers to a series of different walls that were constructed, reconstructed and renovated along the northern border of China. Its purpose was to keep away foreign invaders. Qin Shi Huang, the first Emperor of China, began construction of one of the more famous walls in 220 B.C., but it deteriorated with time. Most of the Great Wall we see today was built during the Ming Dynasty starting in 1368. For 200 years, Ming emperors expanded the Great Wall to its current majesty. It is believed that a million men once guarded the Great Wall of China and that up to 3 million people died during its construction.

Features
Early segments of the Great Wall of China were built of compacted dirt, stones and wood. As a result, there are few surviving remains of the early segments. The more recent sections built during the Ming Dynasty are made primarily of brick. This was easier to work with, stronger and lasted longer. There are battlements along the top of the wall that protected soldiers while they fired arrows at invaders. Signal towers were built within view of the next signal tower so that guards could relay communications along the Great Wall and warn of an attack.

Significance
About 4 million people visit the Great Wall of China every year. It is estimated that 100 million people have visited the Juyongguan pass section north of Beijing known as the Badaling. This is the most heavily visited area. The Great Wall of China is considered a "must see" by virtually every world traveler. In 1987 it was named a UNESCO World Heritage Site.

Misconceptions
It is widely believed that the Great Wall of China can be seen from the Moon. This urban legend began in 1932, when "Ripley's Believe It or Not" made the claim. This was more than 37 years before the first Moon landing, so naturally no one actually knew. None of the 12 men who have been to the Moon said they could see the Great Wall of China from there. Even astronauts that have looked for the Great Wall from low Earth orbit say they cannot see it with the naked eye.