Apse

Webster's Dictionary of the English Language

·noun The bishop's seat or throne, in ancient churches.

II. Apse ·noun A reliquary, or case in which the relics of saints were kept.

III. Apse ·noun A projecting part of a building, ·esp. of a church, having in the plan a polygonal or semicircular termination, and, most often, projecting from the east end. In early churches the Eastern apse was occupied by seats for the bishop and clergy.