A nondescript green door at the end of a cul-de-sac features a stunningly well-framed, if comically tiny, view consisting of two nation-states and one country, with the dome of St. Peter's perfectly situated in the center.

The doorway in question leads to the Priory of the Knights of Malta, the legendary crusader knights and religious order. Although the property has been in their hands for centuries, the site has seen many occupants. It originally held a fortified palace belonging to Alberico II, the ruler of Rome from 932-954, then became a Benedictine monastery before passing first into the hands of the Knights Templar in the 1100s, then finally to their brothers in arms, the Knights of Malta, in the 1400s.  As it holds extraterritorial status, it is not technically "Italy" within the walls.

The elegant building seen today is a small church known as Santa Maria del Priorato. It is the 18th-century handiwork of the famous architect and engraver Giovanni Battista Piranesi, also known for his romantic etchings depicting the city and for his dark and enigmatic series of imaginary prisons (Carceri d'Invenzione). The church’s architectural motifs evoke ships and the sea, inspired by the longstanding tradition of comparing the Aventine Hill to a ship. The design also incorporates many esoteric and Masonic symbols. Piranesi was buried at the Priory after his death in 1778. The estate also houses the Embassy of the Order of Malta to Italy.

The keyhole vista lines up perfectly with the garden, centered on the Vatican in the distance. No one seems to be able to say with certainty whether this was a beautifully planned peepshow—or just a lucky coincidence.