Typically, this is done through teleportation.
You create an area on the map that's the "inside" of whatever building you want, then you use regions and a trigger or two to teleport the unit back and forth.
Quite sure.
You could make another map for the inside of the building, but there's no way to tell the game to take you from one map to the other. You'd have to do that manually. If you did that, you could use a Game Cache to transfer data as well.
However, if you're looking for something like what occurs in Rexxar's Campaign with the traveling to different areas, you can't do that with a multiplayer map. It takes a campaign.
just make map largest size and set camera bounds so it looks like ur going to a whole different map but ur not, its what Elimination Tournament and most mini-game maps do if you've played them before
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.