According to the Digital Journal, five chimps caused a stir when they built a ladder out of tree branches and escaped from the German zoo of Hannover. No monolith was found.
Hannover Adventure Zoo was temporarily evacuated while the animals were roaming free and police surrounded the premises with orders to shoot any chimpanzee that tried to leave.
The police were not needed in the end.
Four of the five animals "had a quick look around and then jumped pretty quickly back into their compound", said zoo spokeswoman Simone Hagenmeyer.
"The fifth and oldest chimp went off to visit the head gorilla," Mr Hagenmeyer said.