Opened in 1931, the library was designed by James Gamble Rogers as the centerpiece of Yale's Gothic Revival campus. It is elaborately ornamented, featuring extensive sculpture and painting as well as hundreds of panes of stained glass created by G. Owen Bonawit.
In addition to five large reading rooms, a Music Library, and courtyard on the ground floor, the library's tower has sixteen levels of bookstacks containing over 4 million volumes. It connects via tunnel to the underground Bass Library, which contains an additional 150,000 volumes.
According to wikipedia