The shallow U-shape of the Assembly Building is dominated by the Assembly Hall, the biggest room in the Palais which can seat about 2,000 people. The present appearance dates from 1996 after a major renovation.

The Hall was inaugurated on 25 September 1937 during the 18th League of Nations Assembly. It was possibly the first meeting room in the world to be equipped for simultaneous interpretation. The present Hall can provide simultaneous interpretation in six languages.

As the number of UN member nations has grown, the Hall has been regularly refitted – to accommodate the new delegations and to improve its acoustics and technical equipment.

During one of these refits, in the 1970s, the Hall’s original entrance doors – two magnificent bronze doors representing War and Peace, donated by France – had to be removed. They are now found, safely preserved, just outside the Hall on the third floor.

Regular events in the Assembly Hall include the annual meetings of the World Health Organization and the International Labour Organization. The Hall has also hosted occasional meetings of the UN General Assembly (which normally meets in New York).