I guess it's how they stick together
There are bits and pieces of the old Berlin Wall scattered all over the city, and today Tom and I stumbled across a display outside the Bahnhof Potsdamer Platz where there were several of the concrete panels, along with informational signage.
The weird thing is that the panels were pretty solidly covered in what turned out to be chewing gum. I have no idea what's up with that. Is this some kind of weird graf on top of the more traditional graf? Or did someone just start by sticking their gum on the panel, and the idea took hold and now there's ton's of less-than-charming really old gum there?