It includes two main floors and a mezzanine floor. Fifth Formers slept on the mezzanine floor below this. The open interior arrangement allows administrative offices on the mezzanine floor to overlook gallery space. At first, stations were designed without the mezzanine floor. This use necessitated massive arched doors and a mezzanine floor. The reading rooms each consist of double-height rooms with a projecting mezzanine floor. In 1953 WHBQ moved to the mezzanine floor of the Chisca Hotel. Sometimes these were placed on a mezzanine floor, as at Kinross. The additions included a mezzanine floor to both wings. The mezzanine floor is composed of glass blocks. For more than 15 years, coffeehouse chain Starbucks occupied the space on the mezzanine floor. It is equipped with four escalators and a cafeteria on the mezzanine floor. The mezzanine floor of the library houses the Galangue Room. A mezzanine floor at cornice height was used for storage. A mezzanine floor has been added to the southern end.