A sweeping view of Rome is perfectly contained in the keyhole of a non-descript looking door on the Aventine Hill, neatly placing the dome of St. Peter's right 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 becoming 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.
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 his enigmatic and dark series of imaginary prisons (Carceri d'Invenzione). The architectural motifs in the building evoke ships and the sea, inspired by the longstanding tradition of the Aventine Hill being compared to a ship. The design also incorporates many esoteric and Masonic symbols. Piranesi was buried at the Priory after his death in 1778.
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.
The gardens themselves can be viewed by appointment only.