Uris Hall
Uris Hall houses Columbia Business School, as well as the Uris Deli and a loud library, the Business & Economics Library.
There are also top secret meeting rooms there, but they're secret, so I can't write about them here. Perhaps the kind of places where one might find Bain Lehman, the bastard love-child of Merrill Stanley and JPSachs.
When it was built, it was so ugly that Architecture students picketed its dedicated.