Walls that separate Catholic and Protestant neighborhoods in Belfast are called Peace Lines.
Here are some multimedia features about them:
Still Divided is an audio slideshow from The Guardian.
Peace Walls of Belfast is another slideshow from The Guardian.
Here’s another slideshow.
Thanks to Ira Socol for writing about them. I had never heard of these walls before.
I’m adding these links to The Best Sites To Learn About Walls That Separate Us.