The original structure of the fortress of the Saint-Angel castle, as well as the bridge of Elio (called today the Saint-Ange bridge), were established by the Demetriano architect between 117 and 138 after JC, like mausoleum for the family of the Adrian emperor. At the top, the statue of the Emperor, personification of God of Sun.
In 271, however, defensive bastions are added on the outpost of the walls of Aureliano on the shore of the Tiber.
In 1277, the castle becomes the property of the church which decides its completion into a fortress prison and establishes connection with the buildings of the Vatican by the secrete way of the "passetto".
The name of "Saint-Angel castle" comes from a miraculous appearance during the plague of 590 where according to the tradition, the pope Gregorio Magno, praying in the procession, would have had the vision of an angel which lowered the sword, and it would have interpreted this gesture as announces disappearance of the plague in the sector.
In memory of this event, a statue in wood was placed at the top. It known various versions, of which some out of marble, then out of bronze. The latter which was molten in 1527 to forge guns. The current statue, the sixth, comes from the work of the Werschaffelt artist in 1753.
The interior of the building, is made of five floors and includes, in more of the many rooms of the Roman era, various rooms with frescos of the Renaissance (Rebirth).