The outline is instantly recognizable. A wavy line snaking upwards with two or three boxes placed on it at intervals means the symbol of China - the Great Wall. You will find this picture not only on tourist souvenirs but also on "daily needs" like tea, soap and pencils. So you cannot travel to Beijing without visiting it at either of its most accessible parts.
When and where to go?
As it's an open air site, you can visit it for a small fee any time of year but the steep slopes are slippery in winter and you need to carry your own weight in water in mid-summer. So try for May or September. Whatever day you choose, you will certainly not be alone. Most people go to the Badaling Pass, 75 km from Beijing, but the section at Mutianyu is worth making the small extra journey for. It involves a beautiful drive eastward through villages and mountains. After restoration it opened to tourists in 1986 and if you are really energetic you can climb beyond the restored section and see the wall in its natural state of decay. The path up to the wall at Mutianyu takes at least twenty minutes (You _can_ cheat and use the cable car) and it's about ten minutes up from the car park at Badaling if you turn right. (Turning left brings you suddenly to a very steep climb with knee-high steps, although it's not impossible on crutches.
You can get there by bus or train but a guided coach tour from your hotel works out only slightly more expensive and cuts a lot of hassle. It's a good idea to take low denomination US dollar bills with you. Heavy recent American tourism means that the souvenir sellers won't accept anything else. Bargain fiercely if you really want something (like the stunning patchwork quilts). If you have enough time in Beijing, it's probably better to buy anything except postcards ($1 for a set) at the Friendship stores in town.
In the 5th century BC the Warring Kingdoms in northern China built many small walls. Under Shi Huangdi, the first Qin emperor, these were joined together to form a single Greeat Wall to defend his unified kingdom against the northern barbarians. Of course, the wall was only as strong as its defenders and they couldn't stop the Mongol invasion. But once the Ming overthrew the Mongol Yuan dynasty, wall-building really took off. This was when the wall as we can see it took shape. Most sections date from the Ming period (1368-1644) when the wall was extended to its present length (ten thousand li = about 3,000 km) and fortified.
Out of this world?
And is it the only man-made structure you can see from the moon? It's long enough certainly, but have you ever seen a picture of it from outer space? 1It's certainly worth "mounting" the Great Wall from ground level. Enjoy your trip.