Today, and after the completion of a new wing in 1973, it is the second most important centre of the United Nations after New York.
The building itself from outside is not worth visiting. I could not take a guided tour (not aware if there is a tour). Since its an important stage in world politics, you may visit to put t tick in the box – yes, I have been there and done that!
We walked down to the UN from the Geneva central rail station and it was a long walk. Best thing would be to take a bus.
Location: Avenue de la Paix