translucent concrete
light transmitting concrete, in block form, available from litracon is now on display in washington dc at the national building museum. this is fun stuff.
apparently invented by aron losonczi, litracon embeds optical fibers in the concrete to allow light to pass through the building material. this reminds me of a thing i ran into several years ago, while researching the history of an old building. the architect, one charles emmett cassell, apparently patented a way to bring light into basement floors of buildings through glass embedded in the sidewalk. that was 19th century whiz-bang technology, so welcome to the 21st century.