The above equation shows how tough it is to walk the Great Wall of China. A one-and-a-half-year journey along the Wonderful Wall is a great test of physical strength and fortitude. Ordinary folks will struggle to make the journey. Only those who are determined to see everything that the wall has to offer should consider making the trip. The wall was built by men over many years, using mostly stone and some wood. It stretches for thousands of miles from Beijing in the north to Guangzhou in the south, covering all parts of the country where it is not submerged by water. The wall's history goes back more than 2,000 years, when it was first built to protect China from invasion. Over time, it became more of a symbol of imperial power and prestige than an actual defense mechanism. The last section was completed in 2009, after which time it was opened to the public. You can learn more about the wall at any of its many museums or memorial sites. Or you can simply walk among its remnants and imagine what it must have been like when it was new.