Simple! Easy! The rules are simple – if you had a skyscraper floor, what would you put in it? Why would it be special? Etc! 1st person does Floor 1, next Floor 2, and so on!
Post your posts like this:
Floor #
This floor is home to bla bla bla. Why? Because yadda yadda yadda yadda yadda. Also, it has yabber yabber yabber yabber yabber. It also has yeah yeah yeah in it. Nah nah nah.
Floor 1
This floor looks like an ordinary hotel lobby by day. At night the laws of physics become rather malleable.
This floor has a graveyard where all the good people who died fighting for something good are buried, they all died like heroes, and they can finally rest in peace here
This floor grants a strange calmness to anyone that steps inside. The calmness lasts a short time after leaving, it's duration increasing with time spent in the room.
This floor houses a giant radio antenna. Roughly five times as large as the Warsaw radio mast, it reaches a height of 3250m. Unfortunately, five times the height means five times the wavelength, so only specialized radioastronomy equipment would be capable of detecting its signals. Of course, they can't anyway, because the thick reinforced exterior walls prevent any clear signal from escaping the building, so building it was just an all around terrible idea.
This floor holds the emergency service ward. Should any accidents or incidents occur, emergency personnel will be able to swift act due to personal teleporters. Of course, there are various floors which are off limits to the staff due to various reasons.
This floor is empty. Completely empty. No air, no light, nothing. Only when someone enters or puts something in the room is there any matter or energy within it at all, and any trace particles left immediately vanish after object they came from left.
This floor has another gravitational stabilizer, except that there isn't any free space at all. In order to reach floor 509, you need to exit the building and ascend a series of perilous metal stairs wound around the colossal machine. There are no railings on the stairs either, and the wind gets rather violent this far into the tropopause. Parachutes and mountaineering cables used to be available on floor 506, but they all vanished without a trace.
This floor is filled with the copies of all the people who have visited this floor at least once starting from it's inception. These copies do nothing but wander around meaninglessly.