Why are there giant concrete tunnels in the desert?

I am fascinated though with the way they suspend the instruments so that they're isolated from the surrounding area like I'm an audio engineer so I've learned how and helped build control rooms where the walls and ceilings and floor was isolated from the outside environment so that a truck going by wouldn't create a buzz in the audio but these things are a whole different universe when it comes to sensitivity and I'm very curious I mean I've read how they suspend them kind of but I've never really heard in detail how they construction wise like how they manage to suspend the mirrors and the the particle beam a projectors and what those strings that hang I think maybe they hold the mirrors or but how they actually attach them to the surrounding walls and ceilings and whatnot but without the walls and ceilings affecting the movement of them I'd love to hear some details on how they build these