Look from the middle of the map at the cranes, then to the left side of the map. Go that side's back left corner. You will see broken scaffolding. Sprint from before the ledge and jump to the left outside yellow railing. Note: The railing is vertical. This is a hidden ladder. Climb up this railing/ladder to the top of the scaffolding, then walk to the right of the scaffolding along the ledge of the building. You will eventually reach another scaffolding. Climb onto this scaffolding. Walk to the top. Look towards the building and climb onto the higher ledge. Follow that ledge going left. Keep going forward and you will reach the roof. This is a great sniper position. You may want to bring a Tactical Insertion because other players may discover you on your way to the top, or while you are up there, and lob grenades.