On the Poisson map, there is a barn or house behind a Nazi Tiger Tank spawn. This part of the map is the part where the Nazis usually respawn. Go in and climb the ladder, then walk over to the window in the front. To your left should be some boxes. Back up, get prone, and crawl up to the corner on the left side of the boxes. Crawl until you cannot move further. Then, stand up. If done correctly, you should be apparently on top of the roof. Although you cannot move, you will have a good sniping position. If you prone again you will be back inside the house. You will also have an excellent view on the little town area and the road to the right that leads up to the house that is next to the other Tiger spawn point.