This is an lively Great astronomical narrative video approximately the construction of the Giant Magellan Telescope,the world's largest optical telescope. Each of the telescope's mirrors are around 27-feet tall and weigh around 17 tons, and it takes approximately seven years to produce a mirror (with three years of precision polishing and grinding alone). The telescope will contain a resolving power ten times that of the Hubble Space Telescope, and is estimated to be ready for use in 2025,or approximately four years after an asteroid destroys the planet and all this work was for nothing and we're chilling with the dinosaurs, which is gonna be awesome.
Keep going for the video, and the coolest part of which I thought were the placement and melting of the glass chunks starting at 0:50.
Source: geekologie.com