Semicircular or polygonal termination to the choir, chancel (see cathedral ), or aisle of a public building, first used in pre-Christian Roman architecture.
Originally a large niche to hold the statue of a deity in a temple, the apse also appeared in ancient baths and basilicas . The domed apse became a standard part of the Christian church plan.
Apse, basilica of S. Vitale, Ravenna, 526–547
Alinari
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