The square was designed by the famous architect and painter Giovan Battista Piranesi, a 18th century famous architect and engraver also known for his
romantic etchings depicting Rome, who also realized the palace and the small church called Santa Maria del Priorato, both within the extraterritorial properties.
The beautiful and impressive square has splendid decorations rich in obelisks and military trophies full of symbols and
references and the famous doorway with the keyhole.
The doorway in question leads to the Priory of the Knights of Malta, the legendary crusader knights and religious order. The keyhole vista lines up perfectly with the garden, centered on the dome of St. Peter in the distance.
The Order of the Knights of Malta is one of the last surviving orders of knights left over from the Crusades.
The knights are not in the island of Malta any longer, and their headquarters are now in Rome. They have important properties in the city of Rome: an estate on the Aventine hill, a house located within the Forum of Augustus and a palace on via Condotti.
Being a sovereign order each of the above sites has the right of extraterritoriality, the Italian state recognizes their sovereignty.
In Rome there are three nations: Italy, the Vatican, and the Knights of
The gardens can be viewed by appointment only.