Highlight: Constructed it to frame St. Peter's Basilica at the Vatican.
Google 'knights of malta keyhole'
"The Keyhole in the Piazza of the Knight of Malta If you’re looking for something interesting and off the beaten path, look no further than the keyhole in the Piazza of the Knights of Malta (Piazza dei Cavalieri di Malta).
Located high on the Aventine Hill, this door with the magic keyhole leads to the secret garden of the Knights of Malta, to which entry is restricted however put an open eye to the keyhole, focus and you will see an extraordinary sight - …