part of
two-dimensional continuant fiat boundary
cave
cave entrance
Cueva de Altamira
FTT:444
A two-dimensional continuant fiat boundary which is used to demarcate the interior from the exterior of a cave.
The term "cave entrance" is typically used when ingress or entry to the cave is desired. The same fiat bondary can serve as a cave exit, although that may be less feasible due to the shape or other physical properties of the cave.
cave exit