Lego..

This was the work of Jan Vormann. He "dispatched" mostly holes that remained from the World War II in all over the wall in Berlin especially on some of very touristic spots, (Kupfergraben corner with Dorotheenstraße). People of all ages spontaneously started "helping" him with the dispach work project and plastic construction pieces in all colors, between old stones, gave an interesting new twist in Berlin. Colours are everywhere. It's a lego land...

(source from here)