A trick I heard of to see through frosted glass is to put clear tape on it.

You go all the way to the left until you see a blue building. Climb up the building until you see a vine. Go up the vine. You will see a giant and you will give him the egg. Then the giant will let you through. You have to go through all the junk and climb over the airplane and there's your jetpack

You are referring to Congress Parkway downtown which runs through the old Main Post Office building between South LaSalle Street and South Financial Place.

See related links for map.

exterior?

You can run through the area where the baby zombies are and find the kino der toten building search it on youtube to see what i mean