The white door on the lower right is the entrance to the Vatican Library.  While the library's collection is centuries old, this particular wing of the Vatican dates only to the 1950s.  The much smaller door at the bottom left is the entrance to the "secret" collection.  This photo was taken not far from the entrance to the Sistine Chapel.   Each year the Vatican receives thousands of requests from scholars across the world asking for permission to be a Reader. 

Among the mathematical treasures, one especially appreciates the "P" Euclid, confiscated by Napoleon (1808) and returned to Rome over a century later.   In addition, Paciolo's  "Summa" is a compilation - an encyclopepdia - of all mathematical knowledge known as of 1494.  His work is the first published treatment of double-entry bookkeeping.