Piazza dei Cavalieri di Malta, on the Aventine Hill, was designed by the Venetian print-maker Giambattista Piranesi (1720-78), who is much better known for his etchings of Rome. The piazza (1765) was commissioned by Giovanni Battista Rezzonico, the nephew of Pope Clement XIII (r. 1758-69), and Prior of the Knights of Malta.
The walls on two sides of the piazza sport small obelisks and a set of curious bas-reliefs.
Piranesi also designed the entrance to the gardens of the Priorato di Malta, on the west side of the piazza. The door boasts the most famous keyhole in Rome.