It's the United Nations Secretariat Building facade in the title sequence. It looks like they shot at a different building for the street level scene.
Saul Bass designed title sequence:
http://annyas.com/screenshots/update...itle-sequence/
United Nations Secretariat building, facade detail:
http://www.emporis.com/ photographer: Mathew Shaffer
Seagram building facade detail:
https://www.flickr.com/photos/doctorcasino/7896047262