Want To Make A Giant Telescope Mirror--Here's How
"The world's largest mirrors for the world's largest telescopes are made under the football stadium at the 
University of Arizona."
"Why there? Why not?"
"'We wanted some space, and it was just used for parking some cars, and this seemed like a good use,' says Roger Angel."
"Angel is the master of making big mirrors for telescopes. For 30 years he has been using a method called spin casting to make the largest solid telescope mirrors in the world."
"At the moment, he's making the second of seven mirrors, each 27 feet across, that will go into the Giant Magellan Telescope (GMT), which will be sited on a peak in the Andes Mountains in Chile."