exedra, in architecture, semicircular or rectangular niche with a raised seat; more loosely applied, the term also refers to the apse (q.v.) of a church or to a niche therein.
In ancient Greece exedrae were commonly found in the parts of major cities that had been reserved for worship, such as the Acropolis in Athens. Scholars and poets held discussions in the walled recesses, which were also used for rest and contemplation.
Exedrae were often constructed in Roman buildings, as in the Minerva Medica in Rome, where they were added in the 4th century to strengthen the supports of the heavy dome. Roman exedrae of both rectangular and semicircular design were sometimes topped with semidomes and often fronted with monumental columns or pilasters. In the Pantheon at Rome, for example, three semicircular and four rectangular exedrae were constructed around the main interior wall, probably to house statues of the gods of the seven known planets. The exedra directly across from the entrance is domed; each of the remaining six exedrae is faced with two marble columns. Exedrae were also built outside Rome and Greece; an example can be seen in Istanbul in the 6th-century Byzantine churches of SS. Sergius and Bacchus and St. Irene.