Apse and Caldera

Apse noun - A domed or vaulted recess or projection on a building especially the east end of a church; usually contains the altar.

Caldera and apse are semantically related. In some cases you can use "Caldera" instead a noun "Apse".

Caldera noun - A large crater caused by the violent explosion of a volcano that collapses into a depression.

Apse and caldera are semantically related. Sometimes you can use "Apse" instead a noun "Caldera".