Beinecke Rare Book and Manuscript Library, Yale University.
This building contains the rare books and literary manuscripts of Yale University. One of the largest buildings in the world devoted entirely to rare books and manuscripts, the library has room in the central tower (depicted here) for 180,000 volumes and in the underground book stacks for over 600,000 volumes; it now contains about 500,000 volumes and several million manuscripts.
The building is constructed of Vermont marble and granite, bronze and glass, was designed by Gordon Bunshaft, of the firm of Skidmore, Owings and Merrill. Work began on the building in 1960 and was completed in 1963.
The white, gray-veined marble panes of the exterior are one and one-quarter inches thick and are framed by shaped light gray Vermont Woodbury granite. These marble panels allow light to enter the interior of the building, but filter it such that rare materials can be displayed without damage. I think this brings a rather different and unique perspective to the concept of window for purposes of this thread.
Also, in this photograph I allowed the central core windows to reflect the marble windows in front of it. I find the effect fascinating. Thanks for looking.