mystery

While it only said it was bought by a famous American brand, Ripley's Believe It or Not! later revealed themselves as the mystery buyer in an Instagram post, writing "we're flush with excitement".

The answer to the bubbles mystery turned out to be far from interesting or surprising.

"World Health Organization in touch with Beijing after mystery viral pneumonia outbreak," it says.

And, he added, the discovery does not end the mystery of Kryptos.

“Be careful. We don’t know what mysteries and surprises lie on this island.”