The Pantheon was designed and constructed during the reign of Hadrian in the Roman forum as a temple to all the Olympian gods (Pantheon: "all the gods"). The building consists of a rectangular porch (portico) with two rows of Corinthian columns in the usual fashion of a Greek inspired Roman temple. This porch opens into a massive rotunda (circular room) with the largest unreinforced concrete dome in the world. The original layout of the temple included an enclosed courtyard so that viewers could not see the rotunda from the outside, making the inside seem impossibly and unexpectedly huge. The domed ceiling includes patterns of sunken coffers and a 29-foot wide oculus (central opening) that helps to illuminate the temple. It was dedicated to "St. Mary and the Martyrs" in the 7th century as a Roman Catholic church.
The Church of Santa Costanza was originally built as the mausoleum of Constantina, the daughter of Constantine. It was dedicated as a Catholic church in 1256 to Santa Costanza, which is the Italian name for the later sanctified Constantina. The building has a large rotunda surrounded by a barrel vaulted ambulatory, and displays Composite columns and clerestory windows, giving the interior a divinely lit feel. It also displays complicated mosaics, sculptures, and marble work, contrasting its relatively simple exterior.
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Many examples of early Christian architecture display elements and even near copies of Roman art and architecture. For instance, the Pantheon and the Church of Santa Costanza both exhibit large domed rotundas as their central architectural feature, although they were built for different purposes they have a similar layout. Roman traditions and images were also reinvented for use in emerging Christian traditions. In mosaics in the Church of Santa Costanza, grapevines and putti (naked cherubs) surround a bust of Constantina. The putti drive wagon loads of grapes to pavilions where more putti are making grape juice for wine. The images are traditionally Roman and associated with Bacchus, but are reinvented to suit the Christian context referencing the Eucharist and symbolizing death and resurrection (the trampling of the grapes to be remade into wine). This is just one example of the connections between Roman and early Christian traditions.