【正确答案】The Great Wall is an ancient defense works of China, which took the longest time to build with the largest amount of engineering work in the world. Its construction went on and on for over 2,000 years since the seventh or eighth century B.C. It spread across the vast lands in North and Middle China with its total length reaching over 50,000 kilometers. Therefore, it is known as 'the Great Wall built in over 2,000 years with a total length exceeding 100,000 li'. Such an enormous engineering project is the only one not only in China but also in the world. Therefore, it was listed several hundred years ago along with the Colosseum and the Leaning Tower of Pisa, etc. as the seven wonders of the world.