The first photograph is of Butler Library, famous for its list of great authors across the facade. You'll have to click on the photo to enlarge it, so you can see the authors' names.
The second photo shows another "library," known as Low Library. However, the building hasn't housed books for some time. "No longer a library, Low houses the Visitors Center and the Office of the President, and is used for campus events," according to a university webpage.
Barely perceptible at the top of the facade is a reference to "King's College" (close-up below). According to a page on the school's history, "Columbia University was founded in 1754 as King's College by royal charter of King George II of England."