Bocce di Leone
I found this Bocce di Leone while wandering around Venice as the sun was rising. (I always love exploring a place in the early morning, watching the streets wake up around me. In Venice I also watch the gondolas with their gondoliers set off to work.)
These Lion's Mouths were used during the Republic to make complaints and denunciations against individuals - a concerned citizen put a letter in the mouth, and the State investigated. Significant evidence was required before the State would act, and a signed, rather than anonymous, letter was preferred.
Walk around Venice, and you can still find these - the Doge's Palace, for example, or the Church of St Martin. Wander Venice, and you'll never quite know what you will find.