Places on earth advised not to visit, 6- the secret vatican archive

There are 53 miles of shelves containing documents relating to the Catholic Church, which date back to the eighth century and are located in a hugely protected area in Vatican City.

Some of these documents include a letter in which Mary, Queen of Scots, pleads with Pope Sixtus V to save her from execution. Researchers were allowed to enter the archive in 1881, but permission to enter is not easy.