Unless you have spent your entire life on another planet or have been born in the last 30 years (and have not had any history lessons), you know what the Berlin Wall was. So, I'm not gonna introduce you to that communist atrocity (if you really need that lesson, you can read up on it here on Wikipedia).
You might however not know about the East Side Gallery. That is an open-air gallery consisting of a series of murals painted directly on a 1,3 kilometres long remnant of that Wall on the Mühlenstrasse in the Friedrichshain-Kreuzberg district of the city. It is an officialy protected landmark, "understood as a monument to the fall of the Berlin Wall and the peaceful negotiation of borders and conventions between societies and people".
It is also very heavily visited (over 3 million people per year), so it was not always easy to "shoot" the murals I was interested in, especially the most known one, Mein Gott, hilf mir, diese tödliche Liebe zu überleben (My God, help me to survive this deadly love or the Fraternal Kiss by Dmitri Vrubel, depicting the Sovjet dictator Leonid Brezhnev and the Eastern German dictator Erich Honecker kissing - a painted reproduction of an actual photograph captured in 1979 during the 30th anniversary celebration of the foundation of the so called German Democratic Republic).
You'll find all the works here.