Artist's impression of European Extremely Large Telescope
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What is the European Extremely Large Telescope (ELT)?

20 June 2014 Last updated at 08:11 BST

One million tonnes of rock have been blasted from the top of a mountain in Chile, in South America.

Why? To make a flat spot to build the world's biggest ever telescope, which will have a mirror that's half the size of a football pitch!

It's called - wait for it - the European Extremely Large Telescope, and Nel has been finding out why it's an Extremely Large deal.