Incredible But True
Incredible But True
Human World
History Makers
Cities Of The World
Art And Music
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Plant Life
Fish, Amphibians, Reptiles
Birds and Mammals
Creepy Crawlies
Marine Life
Restless Earth
Earth's Secrets
Changing Weather
Seas And Oceans
Comparisons
Amazing Structures
World Of Inventions
Travelling Around
Mysterious Universe
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Lines Busy
The world's largest telephone switchboard is in the Pentagon, Washington DC, in the USA. It has 34,500 lines, which handle approximately 1 million calls a day.
 
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Incredible But True
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Incredible But True
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Machines And Man