From Ides Of Metropolis:
Nigel moves through the study to open the door and admit
Lois and Clark, who are shown through to the balcony.
Luthor launches another pigeon, shoots. Again, the clay
pigeon shatters. Clark walks to the edge of the balcony,
looks down.
CLARK
What happens if you miss?
LUTHOR
Interesting question, Mr. Kent.
Let's see.
(more)
LUTHOR (Cont'd)
This clay pigeon weighs two ounces.
We are on the one hundred and
twentieth floor, approximately
fifteen hundred feet above street
level. Considering the G force and
the speed... if the object hit the
pavement, or some hapless passer-by,
it would make contact at about two
hundred miles per hour. My guess is
that it would, unfortunately, kill
him or her, instantly.
(beat, with a smile)
I never miss.
So, that's how many stories off the ground it was.
If you meant how many stories the place itself was... No, I don't think that was mentioned. He probably had the 120th floor to himself, but whether or not he had the 119th, as well, I couldn't say. I don't think we ever explicitly saw something that was on a different level. The chapel, for example, could have just as easily been down the hall from the office as down (or up) the stairs.
... Oh, but I seem to recall the reception chamber for the White Orchid Ball (in the Pilot) as being two stories. Not sure, though.
Paul