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.

The word vaccine comes from the Latin word "vacca," which means cow. This name was chosen beacause the first vaccination was derived from cowpox which was given to a boy.

There is enough concrete in the Hoover Dam to pave a two lane highway from San Francisco to New York.

AMAZING FACTS