The technology to create a sunlit, underground, green park is complex. Using
six tubes called collimators controlled by a computer and GPS system, the
system channels natural sunlight 15 feet down through a series of lenses and
suspended reflectors, which then bounce light back onto the anodized aluminum
parabolic curve. The lens-and-curve method of light diffusion is essentially
the same as that used by the James Webb Space telescope--“a large,
infrared-optimized space telescope” that is being developed to observe stars
forming under extreme conditions.
http://www.newyorker.com/online/blogs/culture/2012/09/meet-the-lowline.html
and
http://www.fastcodesign.com/1670806/can-these-guys-really-pull-off-an-underground-park-in-nyc
