A hollow or natural passage under the earth opening to the surface is called a cave.

Here are some other terms that might be used depending on the specific context:

* Cavern: A large cave, often with impressive formations.

* Grotto: A small cave, often decorated with stalactites and stalagmites.

* Tunnel: A passageway dug or blasted through the earth, often for transportation.

* Shaft: A vertical passageway into the earth.

* Sinkhole: A depression in the ground caused by the collapse of underlying rock.

Let me know if you need more clarification or have any other questions!