triforia

In these respects the architect has reversed the old arrangement, as in the original nave the two westernmost bays had open triforia, the others simply containing a shallow arcading.

Bell's Cathedrals: Southwark Cathedral Formerly the Collegiate Church of St. Saviour, Otherwise St. Mary Overie. A Short History and Description of the Fabric, with Some Account of the College and the See George Worley

The deeply moulded arches are somewhat loftier and more acutely pointed than those in the choir, placing the triforia on a slightly higher level, but the triforia of nave and choir are alike in that in both cases they consist of four arched openings in each bay.

Bell's Cathedrals: Southwark Cathedral Formerly the Collegiate Church of St. Saviour, Otherwise St. Mary Overie. A Short History and Description of the Fabric, with Some Account of the College and the See George Worley

But the respective level of these essential members were so different in the old and new works that the only parts of them that could be retained were the windows of the old clerestory, which falls just above the new triforium tablet, and accordingly these old windows may still be seen in the triforia of the transepts, surmounted by the new pointed clerestory windows.

The Cathedral Church of Canterbury [2nd ed.]. Hartley Withers 1908

There are two galleries in the church, one on either side over the Bide aisles (as triforia), to which access is obtained by means of stone stairs.

Architecture News & Discussion - Archiseek.com 2010