buildings

This is my first post on the forums as I have just recently
started dabbling in HL2 mapping. I have had some ideas for a map that
would be located inside and outside the top of a highrise building.
Mainly I was wondering if there are any specific entities or tricks I
can utilize in order to give my map the effect that it is high off the
ground. Again im pretty new at this so any information would be
helpful. Thanks.

Maybe some fog down the bottom if it is that big, also check out this tuton far away buildings, might help:

http://www.snarkpit.com/editing.php?page=tutorials&game=HL2&id=108

Or perhaps you could make a 3-d skybox put the camera above the buildings so it gives the effect of them going down and use fog to make them look like clouds, this way when someone falls an dies they can not be seen, or you could teleport them to a black room in the map where they woudl die "if done correctly works perfect"

heh, just use the citadel skybox! you know, with the city map on the bottom? and you could add some fog, too.

or what you could do is to create a sky camera entity within a small
sky box below ur map this will project whatever you put into it for
instance i made a dam for my map and it turned out ok.