Titled "Lux in Arcana (Light in the Secret) -- The Vatican Secret Archives Reveals Itself," the exhibition is being held at the city's Capitoline Museums.
It contains manuscripts, parchments and registers which are usually only viewed by scholars who have obtained special permission from the Vatican.
The exhibition includes written exchanges between a long succession of popes and various world leaders and famous historical figures, including Italian Renaissance master Michelangelo, French Enlightenment author Voltaire and U.S. President Abraham Lincoln.
Other documents on display are related to the separate heresy trials against astronomer Galileo Galilei and the warrior priests of the Knights Templar.
The exhibition is scheduled to run until September.
The Vatican Secret Archives, a collection spanning more than 1,000 years, are stored in climate controlled chambers in Vatican City.
Interest in the archives has increased in recent years among the general public after they formed one of the key settings of U.S. author Dan Brown's international bestselling novel, "Angels and Demons," which spawned a Hollywood film of the same name.
The book deals with a fictional conspiracy by a secret order, the Illuminati, to destroy the Vatican.
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