The building has a facade of Tennessee marble. McKim took his inspiration from the Villa Giulia, particularly the attic of its Nymphaeum. Further inspiration came from the Villa Medici in Rome, constructed in the 16th century by Annibale Lippi. The exterior walls are made of dry masonry, which allowed the marble blocks to be set evenly, thus requiring a minimal amount of mortar. Tinfoil sheeting was placed between the blocks to prevent moisture buildup. "The Wall Street Journal" reported upon the library's completion, "No other building in Europe or America was ever erected with this care."