I tried to find a layout of the map but cant. When you spawn in the SW corner bye the water tower, if you go to the stairway that takes you to the roof of new construction then continue to cross the wood plank to the adjacent roof where the other smaller water tower is. Cross the second wood plank to the building a lil NW of the small water tower building the cross the 3rd wood plank and your standing on the building. Its right close to the tank you jump on to get over the wall. If you lay down on the roof you cannot be damaged by anything from the air but if you stand up you can be killed. It is the collision detection on the building, the hitbox for the building is too tall.