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.