A 13,000 mile dragon of earth and stone winds its way through the countryside of China with a history almost as long and serpentine as the structure.
一条1万3英里的土石之龙蜿蜒于中国乡野之间，它的历史几乎与其结构一样悠久曲折。
The Great Wall began as multiple walls of rammed earth built by individual feudal states during the Chunqiu period to protect against nomadic raiders north of China and each other.
长城最初是多座泥土夯实的城墙，由春秋战国时期的各个独立封建国家修筑，以抵制中国北方游牧民和其它国家。
When Emperor Qin Shi Huang unified the states in 221 BCE, the Tibetan Plateau and Pacific Ocean became natural barriers, but the mountains in the north remained vulnerable to Mongol, Turkish, and Xiongnu invasions.
公元前221年，秦始皇统一中国时，青藏高原和太平洋成为了国家的天然屏障，但北方的山脉对于蒙古、土耳其及匈奴人的入侵来说显得非常薄弱。
To defend against them, the Emperor expanded the small walls built by his predecessors, connecting some and fortifying others.
为了抵御外敌，秦始皇扩建了之前所筑建的小城墙，把它们巩固强化并加以连接。
As the structures grew from Lintao in the west to Liaodong in the east, they collectively became known as The Long Wall.
城墙起于西部临洮，止于东部辽东，合在一起称为长城。
To accomplish this task, the Emperor enlisted soldiers and commoners, not always voluntarily.
为了完成这项工程，秦始皇征召了士兵和平民，而他们往往不是出于自愿。
Of the hundreds of thousands of builders recorded during the Qin Dynasty, many were forcibly conscripted peasants and others were criminals serving out sentences.
在秦朝记录的成千上万建造者中，许多人都是被强征而去的农民，另外一些则是服刑犯人。
Under the Han Dynasty, the wall grew longer still, reaching 3700 miles, and spanning from Dunhuang to the Bohai Sea.
汉朝时期，长城继续扩建延长至3700英里，从敦煌延伸到渤海。
Forced labor continued under the Han Emperor Han-Wudi, and the walls reputation grew into a notorious place of suffering.
强制性劳动在汉武帝时期持续着，因而城墙被视作受苦受害之地，从而臭名昭彰。
Poems and legends of the time told of laborers buried in nearby mass graves, or even within the wall itself.
那一时期的诗歌与传说描述了劳动者被掩埋于附近的大规模墓地甚至是城墙内。
And while no human remains have been found inside, grave pits do indicate that many workers died from accidents, hunger and exhaustion.
然而城墙内并未发现人类尸骸墓坑，表明那些劳动者大多死于意外、饥饿与疲劳。
The wall was formidable but not invincible.
长城令人生畏却非不可战胜。
Both Genghis and his son Khublai Khan managed to surmount the wall during the Mongol invasion of the 13th Century.
成吉思汗和他的儿子忽必烈曾于13世纪蒙古侵入之际设法攻克城墙。
After the Ming dynasty gained control in 1368, they began to refortify and further consolidate the wall using bricks and stones from local kilns.
1368年明朝执政之后，他们开始使用当地窑中烧制而成的砖与石头重新强化和加固长城。
Averaging 23 feet high and 21 feet wide, the walls 5500 miles were punctuated by watchtowers.
长城平均高7米，宽6米，5500英里的城墙中间隔着瞭望台。
When raiders were sighted, fire and smoke signals traveled between towers until reinforcements arrived.
一旦看到有侵入者，瞭望台之间便会用升起的狼烟与风火传递信号，直到援兵抵达。
Small openings along the wall let archers fire on invaders, while larger ones were used to drop stones and more.
城墙上的小孔让弓箭手能够射击侵入者，而大孔则用于投掷石头或者其它东西。
But even this new and improved wall was not enough.
但即便是这种全新改进的城墙仍然不够好。
In 1644, northern Manchu clans overthrew the Ming to establish the Qing dynasty, incorporating Mongolia as well,
1644年，北方满族推翻明朝建立清朝，同时合并了蒙古。
Thus, for the second time, China was ruled by the very people the wall had tried to keep out.
因此，这是中国第二次被城墙抵御的外族统治。
With the empire's borders now extending beyond the Great Wall, the fortifications lost their purpose.
随着帝国边界扩展到长城以外，这些工事失去了原本的目的。
And without regular reinforcement, the wall fell into disrepair, rammed earth eroded, while brick and stone were plundered for building materials. But its job wasn't finished.
没有了定期加固，城墙失修破损，夯土被侵蚀，砖和石头则被盗窃用作建筑材料，但是长城的使命仍未结束。
During World War II, China used sections for defense against Japanese invasion, and some parts are still rumored to be used for military training.
第二次世界大战期间，中国用部分城墙来抵御日本侵略，一部分城墙仍然被盛传用于军事训练。
But the Wall's main purpose today is cultural.
然而今日，文化才是长城的主要目的。
As one of the largest man-made structures on Earth, it was granted UNESCO World Heritage Status in 1987.
作为地球上大型人工建筑之一，长城于1987年被联合国教科文组织列为世界文化遗产。
Originally built to keep people out of China, the Great Wall now welcomes millions of visitors each year.
长城起初建造用于防御外人进入中国，如今每年都会迎接数百万游客。
In fact, the influx of tourists has caused the wall to deteriorate, leading the Chinese government to launch preservation initiatives.
实际上，大量涌入的游客已导致长城日益损坏，致使中国政府启动保护措施。
It's also often acclaimed as the only man-made structure visible from space.
它也经常被宣称为唯一一处可自太空看见的人造建筑。
Unfortunately, that's not at all true.
不幸的是，这种说法不完全正确。
In low Earth orbit, all sorts of structures, like bridges, highways and airports are visible, and the Great Wall is only barely discernible.
在地球低轨道上，各种建筑物如桥梁、高速公路以及机场均可看见，而长城却若隐若现。
From the moon, it doesn't stand a chance.
从月球上，它则一点也看不到。
But regardless, it's the Earth we should be studying it from because new sections are still discovered every few years, branching off from the main body and expanding this remarkable monument to human achievement.
但无论如何，地球才是我们应该好好研究长城的地方，因为每隔几年都会有新的部分被发现，它们从主体部分扩展开去，不断延伸着这见证人类成就的伟大奇迹。