When seen from above the Great Wall of China looks like a dragon zigzagging over mountain tops. The Chinese call it "Wan Li Chang Cheng" which means "Wall of 10,000 Li". (10,000 li = 5,000 km)

Actually, the Great Wall is 7,200 km long. Height wise, it is 4.5m to 9m. Depth wise, it is 4.5m to 8m. The entire structure was built by hand using stone, bricks, soil, sand, straw, wood, clay or whatever was available depending on the terrain.

Three main Chinese dynasties – the Qin (BC 221-207), Han (BC 206- AD 220) and Ming (AD 1368-1644) – built the Great Wall of China. All had one purpose – to keep out the "barbaric" Huns in the north who frequently invaded Chinese border areas. In all, tens of millions of people labored on the Great Wall. Many died.

Qin Shi Huang, the First Emperor of China, is credited with kicking off this massive project 2,200 years ago. By connecting old sections with newly built ones, the Qin Dynasty erected 4,800km of wall in 10 years – more than one km a day!

After the Qin, the Han Dynasty extended the Great Wall through the Gobi Desert. Watchtowers were added to the walls. Smoke spirals produced by burning wood and straw mixed with wolf dung functioned as an alarm system. One smoke column meant a force of 100 men was attacking; two columns signaled that more than 500 men were approaching, and so on.

The Great Wall of China we know today was built by the Ming Dynasty 600 years ago. By then the ancient wall was in ruins. The Ming rulers rebuilt most of it over a period of 200 years. That the wall is still in good condition today is due to an invention of that era, the adding of rice flour to make super strong bricks and mortar!