This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
What distinguishes the Vatican Museums from a comparable secular collection of comparable scale is that its most famous space has never stopped being used for the purpose it was built for. The Sistine Chapel houses Michelangelo's ceiling and Last Judgment as museum quality art open to visitors, yet it is also the working conclave chamber where the College of Cardinals gathers to elect a new pope, a religious function the museum's public role has never displaced.
That dual character, an ecclesiastical institution administered by the Holy See that is simultaneously one of the most visited art museums in the world, runs through the whole collection rather than the Sistine Chapel alone: the Vatican Library's manuscript holdings and the Raphael Rooms serve both scholarly and devotional purposes at once, assembled over five centuries by a papacy that treated the collection as an expression of the Church's own standing rather than a separate civic undertaking. Its legal status under papal rather than Italian civic authority is not a technicality but the direct expression of that same fact.