Produced and presented by Alessandro Sorbello http://www.alessandrosorbello.com for New Realm Media http://www.newrealm.com.au The Aventine Keyhole For those in the know, this is a popular attraction. Locals bring their visitors here to admire the impressive optical effect created by Piranesi. It doesn't sound that wonderful; some trees and St. Peter's, but few leave uncharmed. Located in the artistic and enigmatic Piazza dei Cavalieri di Malta, a gate bars the entrance to the Priory of the Knights of Malta. Queue up to have a look through the ornate keyhole, and you'll see the Vatican's vast white cathedral floating at the end of a symmetrical tunnel of trimmed trees.