In 1803, Napoleon Bonaparte is alleged to have said, "China? There lies a sleeping giant. Let him sleep! For when he wakes he will move the world." Perhaps, Napoleon was mindful of the fact that a few centuries before, China was the sole hyperpower in the world, much as the United States is today.
In the 16th Century, China began to build a virtual wall, around China, to seal themselves off from foreign influences. By the 19th Century, relatively small European powers, using technologies, many of which originated in China, but refined in the rest of the world, were able to force the establishment of enclaves, in mainland China, where their laws prevailed and not those of China, to the humiliation of the Chinese people.
In history, walls have usually marked the limits of the power of a nation, not something that made a nation great.