Locked door in the Vatican

[VinegarPancake]

I found a door that says "Opens from Other Side" at the bottom of the Sistine Chapel, where you enter from the Borgias Courtyard.

I have beat the game, and I am only revisiting locations to 100% them... I am missing one of the ancient relics here and I thought that might be related (but it could be that I just forgot that I used that door already somewhere in the story). Any help is appreciated!

[Aris]

You can revisit the zone of the last main quest in the Vatican, up until you pick the elevator. This is an exit door of that area.

[VinegarPancake]

Sweet, thanks! I just found my last missing relic there and used the exit.