library is known as the "nave" because it imitates the main approach of a cathedral. At its western terminus is a chancel containing an ornate circulation desk and altarpiece mural painted by Eugene Savage. Constructed of Indiana limestone and Ohio sandstone blocks, the nave is a self-supporting stone structure with none of the steel reinforcement used elsewhere in the library. It is elaborately decorated with stone and wood carving, ironwork, stained glass windows, and ceiling bosses. The main hall is flanked by two aisles, which originally held card catalogs for the library bookstacks. Though the original catalog drawers remain in the aisles, the cards have been removed and the aisles converted to seating areas and a computer lab. At its western end it is intersected by a transept, which leads to the library's main reading room on one end and its wing on the other. For many years, smoking was allowed in the nave, which left a layer of soot on its upper levels. Beginning in 2013, the nave underwent a $20-million, yearlong renovation to clean its surfaces, restore its architectural details, overhaul building systems, and reconfigure visitor circulation and services. Tower Fifteen levels of library materials, primarily books, are housed in the building's tower, commonly referred to as the "Stacks". Originally intended to house 3.5 million volumes, it is a seven-story structure, with eight mezzanine levels interleaved between the main stories. Although encased in a Gothic exterior, the tower's structural system is a welded steel frame, which permits a vertical rise that traditional Gothic techniques would not. The crenelated roof of the tower is elaborately decorated, complete with a castle-like housing for air handling equipment. The tower's shelves are estimated to stretch , contained within of aisles. In addition to the library collections, the tower houses reading rooms, study carrels, library offices, and special collections, including the Babylonian Collection. Access to the Stacks is restricted to affiliates of the university and library patrons. Reading rooms Four reading rooms sit near the nave on the first floor of the library: Starr Reading Room, the main reading room of the library, is at the south end of the library, next to Trumbull College. It is a reference room designed in the style of a monastic refectory. Under a barrel-vaulted ceiling, the room is lined with traceried windows and oak bookshelves decorated with a botanical frieze. A 1998 restoration was funded by