separate the different double bays; smaller buttresses, containing a single pier, divide each double bay into smaller "sub-bays". This alternation of large and small buttresses gives the appearance of four double bays with two sub-bays each, rather than eight singular rectangular bays. At the arcade level, each of the sub-bays contains an arrangement of stained glass with two lancet windows under a rose window. The sub-bays also contain another stained-glass arrangement at clerestory level, each with two lancet windows and one rose window. The clerestory arrangements each measure long by wide. Carved parapets, as well as gables with dormers, run along the copper roof. Inside, there are six north–south rows of piers, three to either side of the nave. These piers divide the nave into five aisles running west to east, with the center aisle located on the same axis as 112th Street. There are four smaller aisles, two to either side of the center aisle. Additionally, the interior contains several flying buttresses, concealed by "bridges" that carry them over the outermost aisles. There are sixteen sub-bays in the nave, eight on each side; the easternmost sub-bays on either side contain doorways. Each of the bays are named after some aspect of humanity. From west to east, the sub-bays along the northern side of the nave are named the Sports, Arts, Crusaders, Education, Lawyers, Ecclesiastical Origins (Anglican), and Historical and Patriotic Societies' (American), and Fatherhood bays. The sub-bays on the southern side are named the All Souls', Missionary, Labor, Press (Communication), Medical, Religious Life (Earth), Armed Forces (Military), and Motherhood bays. Each of the sub-bays contain carved parapets atop their mono-pitched roofs. The sub-bays are used for various exhibits. The iconography of the stained-glass windows in the arcade and clerestory is related to the theme of each respective sub-bay. In each sub-bay, between the lower windows and the clerestory windows, is the triforium level, which contains two west–east corridors with numerous windowless rooms and office spaces. Apse The apse, located at St. John's eastern end, is made up of numerous components. The center of the apse contains the choir, located below the great organ. Two ambulatory passages run adjacent to the choir, one to the north and the other to the south. Seven chapels, a baptistery, and a columbarium are also located in the northwestern part of the apse. The apse contains two sets of clerestory windows: the large ambulatory