Last November, on business in Beijing, I visited the Great Wall of China with my friend Larry. It was a crisp, cold day with blue sky and a phantastic view over the hills, along which this enormous wall crawls like a big, neverending caterpillar.
Both Larry and I had forgotten our digital cameras, so we took pictures with a disposable Kodac camera. Larry then scanned the pictures for me.
The trivia below is copied from wikepedia.
The Chinese were already familiar with the techniques of wall-building by time of the Spring and Autumn Period, which began around 8th century BC. During the Warring States Period from 5th century BC to 221 BC, the states of Qi, Yan and Zhao all constructed extensive fortifications to defend their own borders. Built to withstand the attack of small arms such as swords and spears, these walls were mostly made by stamping earth and gravel between board frames.
Qin Shi Huang conquered all opposing states and unified China in 221 BC, establishing the Qin Dynasty. Intending to impose centralized rule and prevent the resurgence of feudal lords, he ordered the destruction of the wall sections that divided his empire along the former state borders. To protect the empire against intrusions by the Xiongnu people from the north, he ordered the building of a new wall that connects the remaining fortifications along the empire's new northern frontier. Transporting the large quantity of materials required for construction was difficult, so builders always tried to use local resources. Stones from the mountains were used over mountain ranges, while rammed earth was used for construction in the plains. There are no surviving historical records indicating the exact length and course of the Qin Dynasty walls. Most of the ancient walls have eroded away over the centuries, and very few sections remain today.
The Great Wall concept was revived during the Ming Dynasty, following the Ming army's defeat by the Mongols in the Battle of Tumu in 1449. The Ming had failed to gain a clear upper-hand over the Mongols after successive battles, and the long-drawn conflict was taking a toll on the empire. The Ming adopted a new strategy to keep the Mongols out, by constructing walls along the northern border of China. Acknowledging the Mongol control established in the Ordos Desert, the wall followed the desert's southern edge instead of incorporating the bend of the Huang He.
Unlike the earlier Qin fortifications, the Ming construction was stronger and more elaborate due to the use of bricks and stone instead of rammed earth. As Mongol raids continued periodically over the years, the Ming devoted considerable resources to repair and reinforce the walls. The sections near the Ming capital of Beijing were especially strengthened.
Towards the end of the Ming Dynasty, the Great Wall helped defend the empire against the Manchu invasions that began around 1600. Under the military command of Yuan Chonghuan, the Ming army held off the Manchus at the heavily fortified Shanhai Pass, thus preventing the Manchus from entering the Liaodong Peninsula and the Chinese heartland. The Manchus were finally able to cross the Great Wall in 1644, when the gates of Shanhai Pass were opened by Wu Sangui, a rebel Ming border general. The Manchus quickly seized the Ming capital of Beijing, and subsequently defeated the remaining Ming resistance to establish the Qing Dynasty.
Construction and repairs of the Great Wall were discontinued under the Qing rule, as China's borders extended beyond the walls and Mongolia was annexed into the empire.
