Go to the map in Spectator mode and look for a drivable tank to the left and in front of two trucks. From there, it should be next to the destroyed building you are looking for. Make sure the truck behind the tank is in front of a destroyed Flak cannon; the building is to the left according to the direction of the tank. After finding the building, notice that the walls are divided into squares or segments. Also note that the correct building is connected to a series of buildings. Line up the tank exactly with the square segment it is next to on the building. Then, look carefully at the shadows and notice how they fade out the walls. If you look carefully enough looking at the whole wall square you can see a chicken with its wings in the air with big bulging eyes. Two segments over you should see a fat pig standing up and smiling.