caverns and towers

The books are hidden at the University of Chicago's new Joe and Rika Mansueto Library:

Beneath the library, a 50-foot-tall cavern holds the equivalent of 3.5 million volumes ... A team of librarians load the books, about 100 at a time, into 24,000 bins that are tagged with barcodes and kept on huge storage racks that sit directly underneath the library. Five cranes work together to bring bins to the librarians when a student or faculty member requests an item. The whole process should take less than five minutes ...
On the other hand, books are what you see in Marta Minujin's 25-meter Tower of Babel. It's constructed of 30,000 volumes in languages from all over the world.