The Castel Sant'Angelo was originally the tomb of emperor Hadrian and subsequent emperors until around ~400 AD, when it was turned into a fortress. Much of the fortress was destroyed and looted by the invading German tribes when they sacked Rome in 410. It was sacked again a hundred or so years later by another German tribe. Eventually it was used as the residence of the Popes, and even had an walled passageway connecting it to the Vatican City across the river. Now it is a museum where you can get nice views of Rome.
This is from the tower overlooking the Tiber river.
This is what the Mausoleum theoretically looked like.
One theory of the Castle's name was that it should be Castel Sant'Angle, because of the river bend. A papal typo caused the error which still propagates today.
The papal seal includes the keys of St. Peter.
where did I see that before???
A pretty kitty, for all you redditors!
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