At this point in the game, you're on the roof of the museum and there is actually quite a bit of combat going on in the streets below. Striders stomping around, rebels running here and there, a few Combine troops scurrying about. It's a neat part of the HL2 street war that there's always combat going on nearby but sort of outside your zone of influence (you can shoot down on the street or lob grenades or whatever, but you're usually too busy dealing with your own problems). You're obviously the center of the game, but it makes you feel like this war is going on whether you're around or not.