5. Vatican Secret Archives| Vatican City
It is perhaps the most private library in the world. It contains the personal documents of all the popes dating back to the 8th century. The archives also contain the state papers, correspondence, papal account books, and many other documents which the church has accumulated over the centuries. Well, Despite the name, the actual archives are not that secretive. You can view any document you want. The only condition being you cannot enter the Archive. You can request for a document and it will be supplied. The Vatican Secret Archives have been estimated to contain 52 miles (84 km) of shelving, and there are 35,000 volumes in the selective catalogue alone. The only documents you can’t access are those which are not yet 75 years old (in order to protect governmental and diplomatic information). Indexes are available for people who want to see if a document exists in the archives.