Deliberate mistake: There are no lights ever to be found in the underground world and the ceiling is literally the surface's ground, but there is still a perfect level of lighting regardless.

Beneath the Planet of the Apes (1970)
Plot summary
Directed by: Ted Post
Starring: James Franciscus, Kim Hunter, Maurice Evans, Linda Harrison
In an effort to find the missing astronaut Taylor (Charlton Heston), James Fransiscus goes on a rescue mission to the planet of the apes. Using the information he receives from the ape village that Taylor escaped from, Brent locates him in an underground fortress in the forbidden zone guarded by telepathic humans.
Mendez: Glory be to the Bomb, and to the Holy Fallout. As it was in the beginning, is now, and ever shall be. World without end. Amen.
Trivia: A bullet from a rifle Charlton Heston owned was the inspiration for the design of the Alpha-Omega Bomb.
Question: When Taylor investigated the rocks, he aims the butt of his rifle at the rocks and then he fades through the rocks and he vanishes. What exactly was the cliff he fell through? Was it a hologram or a mirage or something?





Chosen answer: The mutated humans (the ones with the bomb) have telekinetic powers and projected the image into Taylor's mind, the same way they did with the fire with the apes.
Bishop73