We all know it’s rude to peep through keyholes, but there are some exceptions. There is a nondescript green door in a cul-de-sac in Rome that holds a semi-secret. When peering through the keyhole, you get a perfectly framed view of the dome of St. Peter’s. The door is in the Priory of the Knights of Malta and was originally the fortified palace of Alberico II who ruled Rome between 932 and 954. It was also a Benedictine monastery, ending up in the hands of the Knights of Malta.