Although the Stegosaurus dinosaur was over 9 metres long, its brain was only the size of a walnut.

Dinosaurs ruled the Earth for over 160 million years, from the Triassic period around 230 million years ago through the Jurassic period and until the end of the Cretaceous period around 65 million years ago.

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.

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