Door to the Villa of the Grand Master of the Sovereign Military Order of Malta. This villa on the Aventine Hill was designed by Piranese in the 18th century. The Order of Malta was founded in 1113 as the Knights of St. John of Jerusalem or Knights Hospitallers, to protect and care for pilgrims to the Holy Land.
Looking through the keyhole of the door you see this view of the dome of St. Peter's Basilica.
Thus saith the Lord of Hosts:-Yet once a little while and I will shake the heavens and the earth, the sea and the dry land; and
I will shake all nations; and the desire of all nations shall come.
From Handel's Messiah: Part I