EDIT:Back! okay now to the trick.... On Authorized Personel Only(i think... its the first outdoor area...) head out and you will see a slope-ish pillar... head up that pillar and go to the end of the top and head for the top of In Amber Clad follow it to the back and jump across the gap. and keep going , soon you will reach the second outdoor area but with no enemies , door and etc. go along the side of Cairo until you reach the otherside of the MAC gun at there go down towards the 2nd outdoor-like area and then walk around suddenly from one of the slopes you will float rather then go down the slope! provided the roof-like stuff is fake! you can pass right through 'em!!(psst... remember to go into the yellow windows and crouch...
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