Contrary to what you might think from our frothing immigration debate, the U.S.-Mexico border has a lot of walls – has had for many years.

The Tijuana-San Diego border has two walls, in fact; one runs for 14 miles or so. The second, which runs for a couple miles, is about 50 yards into U.S. territory and looks a lot like perimeters at many California prisons I’ve visited.

The first wall is brown corrugated iron. It runs exactly at the line between the two countries, breaking only for two border crossings. It begins 50 yards into the Pacific Ocean surf, runs along a highway, then several tough looking slums, past the Tijuana airport and ends at the very tall Nido del Aguila mountain.

It was built in 1994. Since then, on the Mexican side, the wall has been a blank canvas for artistic and political expression.

Here’s some of what I found when I walked parts of it recently.