China. This is rough terrain, okay. And they didn't have tractors or bulldozers. They did it with sweat and blood. Oh and the weather, not blistering hot but bone chillingly cold (high winds and heavy snow). And the length: 3,946 miles. Built during the 14th century. They built this wall for defensive purposes, and you know what? IT WORKED!!
Contrast the United States. The US/Mexico border is only about 1,400 miles long. We need to build a wall for "defensive" purposes, too. And you know what? IT WILL WORK. We won't keep everyone out, but we will stop the great majority. Let's say 10% make it over. 100,000 is a lot better than 1 million. But we hear excuses: It won't keep everyone out so don't do it, they say. From our President and from our Senate, both Republicans and Democrats. I'm surprised we have the political will to get up in the morning. What is driving our political stupor? Oh, I remember. Greed!