A crater in the Turkmen desert has been burning for around fifty years, and millions of people know exactly how it started. The problem is that the story does not appear in a single document, and the geologists who worked there tell it differently.

For generations the villagers of Shiyan Beicun believed their ponds were bottomless. In 1992 four of them bought pumps to find out, and drained the water off the roof of a hand-carved hall the size of a church. Twenty-four of them have now been opened, and not one line of Chinese history mentions that they exist.

Across the highlands of northern Laos stand thousands of carved stone jars, some weighing fourteen tonnes. A French archaeologist called them tombs in the 1930s. Then the bombs fell, and it took eighty years to get back to the question.

In July 1970 a US test missile carrying radioactive cobalt came down four hundred miles inside Mexico, and the American army built a railhead, a road and a camp to take it home. What stayed behind in the Chihuahuan Desert was a story about radios that will not work. Here is the documented record, and exactly where it runs out.

Ninety-two artificial islands sit in a lagoon off Pohnpei, walled with basalt logs that weigh up to fifty tonnes each. Dating puts the first courses at around 1180 CE. Nobody has yet explained how the stone crossed the island and floated onto the reef.

A 250 hectare wood on the edge of Cluj-Napoca is routinely called the most haunted forest on Earth. Behind the label sit four photographic negatives from August 1968, a circular clearing where trees will not grow, and decades of measurements that were never published. Here is what can actually be documented, and what cannot.

A magazine writer drew a triangle on the Atlantic in 1964. It took one librarian and two insurance ledgers to erase it.

For over a century, glowing orbs have danced across a Texas desert basin. Physicists traced most of them to a highway. Most — not all.

After heavy snow in 1855, a single line of hoof-like prints was said to run for scores of miles across Devon, over rooftops and haystacks. The deepest mystery may be the record itself.

Since 1795, treasure hunters have poured fortunes — and six lives — into one hole in the ground off Nova Scotia. Nothing conclusive has ever come out of it.

Hundreds of giant figures were etched into a Peruvian desert two thousand years ago. We know exactly how they were made. We still don't know why.

Half of Minnesota's Brule River plunges into a hole in the rock and vanishes. For a century, everything thrown in disappeared without a trace — until two hydrologists tried the simplest test of all. One question, though, was never fully answered.