a room dedicated to take in the views
Sky Garden in 20 Fenchurch Street, London. source: Robert Pittman at Flickr.
Just like we have auditorium as a classy word for a room for hearing, we need a word for a room that was made to take in the skyline views. Technically that word ought to scopetorium (as in: scape room) but since this is a skyscraper dictionary we want to focus on the height involved. As the latin word altus means not only high but also translates into profound, the term altorium would be a good term for this. Sometimes the name sky room is used for the top floor with-a-view although that term might be better reserved for a room dedicated of looking up to the stars.
What we are talking about here off course is the highest room in a skyscraper, or even on top of a skyscraper, primarily dedicated the best and most exclusive views the building has to offer. Every skyscraper ought to have one, really.
Typically, observatories, top floor party halls or restaurants are good examples of altoria. I recent example of an altorium is the recently opened Sky Garden in the top the 20 Fenchurch Street building in London (see above).