I have been in this library in NYC many years ago, it is stunning, and massive inside, this is just a small view of one of the map reference rooms:



Going by the people in some of the photos, the lower part of the ceiling appears to be around 16 feet high, and the center upper rectangular area maybe 18 feet high, that would make a room box around 20" high which is large but not unmanageably so. I don't know what the width and depth of the room is.
It looks very complicated but actually if all the sum parts of the ceiling are broken down it's easy to see how the various moldings and elements were stacked up like a wedding cake and used in repeats.
The dark brown cornice is made up of repeated scrolled corbels, if I made one and molded it, I can cast all of them either in plaster or resin.
The ceiling also has inset panels with leaf designs and shields, some rectangular, some square and some square but one corner rounded, making one of each of those would make all the rest needed if molded and cast.
There's also what's called a gilloche border, a Greek fret molding, at least one egg & dart molding, bead & reel molding, a large half-round molding bearing fruit and vegetable designs, and a couple of others that make up the rest. There's also the central oval flat area which has a wide border with a repeated leaf and vines design.
Over the extended height round-top windows and doors there is a quarter dome inset in the ceiling which is also divided into triangular inset panels decorated in green, gold and red with designs.
The massive chandelliers would be a tough one to do, and there's at least four of them.
The entry doorway has a massive marble surround with a broken pediment fileld with a shield, and scrolled supports, two double wood doors with raised panels and glass.
The lower walls are mainly covered with bookshelves full of books, and of course there are large long wood inlaid tables and many chairs.
I can visualize making a room like this with the gold ceiling, though all of the books needed to fill the shelves would not be cheap (to do it right, like a model using all quality materials with no shortcuts like printed image sheets of fake books glued to the wall) the chandeliers would also be a tricky one to make or find anything like them large enough.
The chairs that exist in the photo look too modern I'm sure they are not original, not even sure about the tables or the red tile floor.
Well it would be interesting to think about, there might be another room in this library that I like even better, or there may be some old photos showing how it looked before the renovations were done.
This is the massive 1911 main branch of the NY Public Library on 5th Avenue and 42nd street, it's constructed from white marble!
Actually I found floor plans that help at least give the size of that room, plus an article mentions the ceiling is 20 feet high, so I was close with the 18 foot estimate.
The photo was taken just before completion, so none of the statuary or the big marble lions flanking the steps were installed yet when this was shot.
I did find over 500 construction photos in an archive, wow! some of the blocks of carved stone for the pediments were shown one per wagon with a couple of guys sitting on top- the stones weighed 15 tons each.

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The map room is only a 35 x 40 foot room in the corner- actually the corner closest to the viewer on the right.
I have seen pictures of tables, but each room in this building has a different ceiling and different furnishings, the tables I saw had heavily carved ornate legs I think in the shape of griffins or something.
The inlaid tops may have been replaced due to wear over a century of use, but the chairs definitely don't seem ornate enough to be original, and with wear and tear of patrons over 100 years one can expect chairs would be damaged, broken, coming apart.
I want a gilded ceiling like that in my house, 20 feet and all! trouble is I'm a Mrs Thorne type with stuff like this but I don't have Bill Gate's bank account to go along with it
I think this ceiling would not be too bad at all but it would take a lot of planning it out and having some reasonably accurate measurements, which I'm betting because it's a landmark and it recently was restored with a $100 million expendature that photos and more details are available for the finding with a little work.
I feel confident I could do the ceiling, I know Lawbre has many 1:12 scale resin classical moldings and elements too, they may have just a few of the right ones that could work or be bashed and modified to fit, the individual molding elements do not have to be exactly the same as the room anyway, but if I found some that were close or the right size but a little different design, that's fine.
Those repeating moldings like the Egg & Dart or the Greek Fret are a bear to do by hand, but a 2 or 3" section can be made in clay without a huge amount of work and time, and a mold can be of that to cast the footage needed. I try to think like a mold maker on many of these elements because that is the easiest most efficient way to make 6 feet of a tiny molding or 100 tiny corbels- make one and cast the rest from a mold- it's all painted anyway, in this case mostly gold, so the material used doesnt matter- plaster, resin, wood.
The 4 chandeliers would probably be the hardest to either make something that looks right, or find something that's not $500 each, but hey, it's my room if I do it, I can use whatever chandeliers I like in it.
I may make another room once I finish the first one- before thinking of actually doing this map room for sure, I have to research up some info and pics, and also see what kind of moldings Lawbre and others have that might work, and then I can tell how many unavailable elements I will need to create from scratch with clay, I already know those corbels with the swags between them the right size and design are not likely going to be found, so I am pretty sure I'd have to model that at the very least.