They say people in glass houses shouldn't throw stones, but would it make any difference if the house in question was half-buried in the ground and shaped like giant blue egg? Well, probably not, but how cool is this pebble-shaped Great Glass House? It may seem like something out of a dream but it actually exists and is the largest single-span glasshouse in the world. Located in Carmarthenshire, Great Britain and designed by Foster + Partners, the enormous structure contains more than a thousand plant species (many endangered) and utilizes many sustainable strategies like an energy-optimizing computer-controlled heating system, an aluminum glazing system, rainwater catchment and a biomass boiler.