Go to the map in Spectator mode. Look for a drivable tank to the left and in front of two trucks. From there, it should be exactly next to the destroyed building you are looking for. Make sure the truck behind the tank is in front of a destroyed Flak cannon, and the building is to the left according to the direction of the tank. After you find the building notice that the walls are divided into squares or segments. And keep note the correct building is not alone; it is connected to a series of buildings. Line up the tank exactly with the square segment it is next to on the building. 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 should 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.