In Spain where they have walls they often will embed broken glass of different colors (red, blue, green, etc) in the top of the wall. It's attractive in it's way, certainly more so than barbed or razor wire, and I'm sure it will discourage an unsophisticated thief from climbing over. I was told this was common in latin america as well.
the first wall i saw in that configuration of glass on the top was the dupont estate on rt 141 as a kid. my understanding of the powder works there was the mangers houses were built in front of the bunkers facing the factory. safety was a big deal at dupont.