New book - 'Building a Better World in Your Backyard' - on Kickstarter (sponsored friend)
The Reichstag was first completed in 1894 and housed the German parliament until 1933 when it was damaged by fire. Years of war and shoddy repairs left the building scarred. After the 1990 re-unification of Germany construction began to rebuild and upgrade the Reichstag into a symbol of efficiency and sustainability. The new glass dome was designed by Foster & Partners, and was completed in 1999. The Bundestag, the German parliament, meets in the building, which is again the seat of government in Germany.
The dome is 24 meters high and 40 meters in diameter, and is mostly transparent. It was built with 400 tons of glass and 800 tons of steel. A walkway winds around the inside up to the top, where there is an impressive view of Berlin. 
The middle of the dome is an upside-down cone surfaced by 360 mirrors that reflect light into the parliamentary chamber, saving energy on lighting. Inside the cone a heat recycling system gathers energy from the chamber and sends it to toehr parts of the building. More than 300 square meters of photovoltaic cells cover the flat area of the roof, which along with another 3600 square meters of panels in the surrounding area, provide electricity to the Reichstag and three other buildings nearby.
A generator that burns vegetable oil, which is much cleaner than fossil fuels, satisfies heating, cooling, and other energy demands. This reduces carbon emissions by 94 percent from pre-reconstruction levels. Hot water in an aquifer 300 meters below ground stores extra energy, which can be used to heat the building or drive a cooling plant to chill water. The cold water can also be stored underground, and is used to cool the building in the summer. 
The new Reichstag was designed to show Germany’s commitment to sustainable energy and efficient design. It is one of the most energy-efficient parliamentary buildings in the world.