Both the influence of the Roman Pantheon and of the Byzantine pendentive came to bear on the designers of the Italian Renaissance, and the crossings of many churches of the period were covered by masonry domes on pendentives. Between pendentive and dome a circular drum usually was interposed, serving to give greater elevation and external importance as well as a space for the introduction of windows. By the addition of an outer shell, the exterior came to be independently designed for maximum effectiveness, and the placing of a lantern at the top of this outer shell provided an apex for the entire composition.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.