Headquarters of the United Nations However, the UN did reject an unusual "model playground" proposal for that site, instead choosing to construct a play area similar to others found around New York City. The first 450 UN employees started working at the Secretariat Building on August 22, 1950. The United Nations officially moved into the Secretariat Building on January 8, 1951, by which time 3,300 employees occupied the building. At the time, much of the Secretariat Building was still unfinished, and the bulk of the UN's operations still remained at Lake Success. A centralized phone-communications system, was built to facilitate communications within the complex. The
Headquarters of the United Nations the complex opened in 1950, were expected to take about 7 years to complete. When completed the complex is also expected to be more energy efficient and have improved security. A temporary $140 million "North Lawn Building" was built to house the United Nations' "critical operations" while renovations proceeded. Work began on May 5, 2008, but the project was delayed for a while. By 2009 the cost of the work had risen from $1.2 billion to $1.6 billion with some estimates saying it would take up to $3 billion. Officials hoped the renovated buildings would achieve a LEED Silver rating.