This hill is known as Aventine Hill, and its secret is a keyhole revealing a beautiful view of Saint Peter's Basilica's Dome. The keyhole can be found in a door to the Priory of the Knights of Malta which is right beside the orange grove. Before the knights of Malta, it used to be the property of Rome's 10th-century ruler Alberico II, as well as a Benedictine monastery and Knights of Templar's home. If someone made it on purpose so that the dome can be seen through the keyhole it must have been basilica's constructors, though it is rather doubtful. No one knows for sure, but it most likely seems to be a miraculous coincidence. If you want to impress your fellow travelers with some knowledge of the city's hidden secrets, show them the spot. The best time to go is summer when the bougainvillea is in bloom.