Floor plans, sections, and an illustration showing the stacks at the New York Public Library.
When the New York Public Library opened in 1911 the skeleton bookcases were the largest in the world, holding 4,500,000 volumes! If laid end to end, the shelves would reach from New York to Philadelphia!
The main stacks are made up of seven levels, each 7' 6" tall with deck floors of 1 1/2" marble. The main stack contains 98,000 adjustable and 16,000 fixed shelves. In addition to the original stacks is an extension under Bryant Park, which extends all the way back to the fountain and features compact shelving so more books can fit. The stacks connect to the library using a 62-foot long tunnel. Recently the library installed a new conveyor belt system that allows researchers to retrieve books from the stacks under the Bryan Park green in just minutes.
But this isn't even enough space for the entire collection, and NYPL has an offsite facility in Princeton New Jersey that holds another three million items. Previously the library organized the books by subject, but to make more efficient use of the space and to eliminate the need for shifting books as new materials arrive, they now organize by size and year of acquisition. Today the collection contains over 15 million items!