In some places along the border there is a barrier that separates Mexico from the United States.
At Tijuana, Mexico, a ten-foot-high steel wall separates the two countries, a wall that people climb over every day.
There has been talk of building a barrier across the entire two-thousand-mile border, something like the Great Wall of China. But the project would be expensive and, to some, a sad comment on relations between the two countries.
