Apse

Holonyms: church, cathedral

Meronyms: ambulatory, apse chapels

Near-synonyms: chancel, presbytery, sanctuary (all broadly synonymous)

Our private tour of the cathedral even allowed us to walk through the apse, which most tours don't.

The draughtsman could not have held the sheet with the apse at the tip, for then, instead of shading away from the edge, most of his hatched lines would begin in the uncharted middle ground of a shadeable area, to strike against the contour; […]

The college has an apse that once held a small chapel.