Undoubtedly the place had been, or was, some cave opening, natural in these heights to begin with.

Returning to camp, they come across a narrow cave opening.

You are behind the big rock at the cave opening.

The cave opening was high enough for him, but not by much.

He stood up and started for the cave opening.

Tom's group started for the shallow cave opening but changed their minds.

Now where its lower end had been, the dark triangle of a cave opening was revealed.

They disguised the cave opening, but in such a way that I could still find it.

Data, roll these large boulders in front of the cave opening.

She ran to the cave opening and into the sunshine.