A 500-metre (1,640 ft) helical walkway ascends the full ten stories. At the top is an exhibition and meeting space called "London's Living Room", with an open viewing deck that is occasionally open to the public. The walkway provides views of the interior of the building, and is intended to symbolise transparency; a similar device was used by Foster in his design for the rebuilt Reichstag (parliament), when Germany's capital was moved back to Berlin. In 2006 it was announced that photovoltaic cells would be fitted to the building by the London Climate Change Agency.