Erich Lessing/Art Resource, N.Y.

JUDGMENT DAY. A grotesque and voracious Devil devours sinners in this 13th-century mosaic in the cupola of the Baptistry in Florence. This Baptistry is an octagonal structure that stands opposite Florence’s famed cathedral, the Duomo. The Baptistry, as its name indicates, is where baptisms were conducted and is perhaps best known for its bronze doors which contain a series of scenes by Ghiberti known as “The Gates of Paradise.”

This fantastic image well captures the vivid visions in the Book of Revelation, a book whose cryptic pronouncements have long baffled readers. One element of that book is now clearer, however: When Revelation’s author addresses the faithful in Pergamon and refers to the place inhabited by Satan, he was thinking of the city’s most grand and well-known monument: the Great Altar to Zeus.