The renovation of the UN headquarters in New York, US, is expected to be complete in 2012 following five years of extensive upgrade works.
The $2bn renovation aims to cut energy consumption in half and reduce carbon emissions by 45%, while equipping the building with measures against terror attacks.
Works undertaken include addition of a new façade to the 39-storey secretariat building, with exterior work beginning in October and taking 18 months to complete.
The low-rise general assembly building will also be completely restored with new screens and air-conditioning systems.
The UN complex consists of six buildings covering 2.6 million square feet. The renovation project will be delivered by Michael Adlerstein.