With 70 miles of shelving and over 6 million volumes, Firestone is Princeton's largest library. When it opened it was the largest open-stack library in the world: unlike many large libraries you can actually go down and explore the shelves in Firestone. The quest for a book leads to a shelf full of related books or books by the same author.
This picture was taken on a cold winter evening on one of the last days in December 2008. I think it captures well the warmth of the interior of Firestone library.