Vatican Secret Archives 

Latin name is Archivio Segreto Vaticano

Part of these archives became available to certain scholars as of 1998.

It is said to have over 40 miles of shelf space.  It is said to contain the proceedings of the trial of Galileo and the records of King Henry VIII, who wanted an annulment of his first marriage.

Other parts are still secret.

Why should a church have secrets?

What are they hiding?

Of course the Vatican is also a government so it is entitled to have secrets with respect to dealings with other governments, but there should be no secrets related to scripture or anything religious in nature.  As a very good rule of thumb no government should ever be trusted!

Perhaps the secrets exist because the Church is hiding something from those who give their money to the Church.  Or does simply saying that there are secrets make membership more desirable?

Could the Catholic Church be founded on something that may not be true?  See a comment attributed to Pope Leo X during the 16th century.