What's 500 metres wide, costs £130 million and moved 9,110 people out of their homes in China?
Come on. You know this...
It's the Aperture Spherical Radio Telescope (FAST for short), the world's largest radio telescope that has just been completed in the remote hills of the southwest province of Guizhou, China.
It's hoped the vast telescope - so sensitive that the authorities displaced the local population to cut down on electromagnetic interference - could pick up any radio waves given off by distant life, passing UFOs or... you know, space stuff.
Construction started back in 1994, with the final massive reflector panel - one of 4,450 - laid in place this weekend.
Don't get too excited about hearing any alien chatter from September though: the massive dish will take around two or three years of fine-tuning before it can start accurately listening to the stars, hoping to pick up any signals sent our way from distant civilisations.
Give it a few years and we'll probably see Hiddleston's 007 running amok around it when it's inevitably used as a future Bond lair.