Used for water distribution, the Delaware Aqueduct in New York, USA is the longest tunnel in the world (as of 2010). Drilled through solid rock, it reaches a staggering 137 kilometres (85 miles) in length. More tunnel facts.

To lose one pound of fat, a person has to burn approximately 3,500 calories.

The fingerprints of koala bears are virtually indistinguishable from those of humans, so much so that they can be easily confused at a crime scene.

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