One of my favourite scenes in Indiana Jones and the Last Crusade is the Library Scene. It totally plays up the fact that Venice is an old city, and that things like churches are sometimes reused for other things, like the library. Does X mark the spot? Is there hidden knowledge in a crypt under the library?
What kind of other knowledge is hidden in out of the way places like that? What kind of deviant cults that seek out the Simulacrum might exist in Venice? Are there Deep Ones in the waters?
Dont forget that Italian count Boniface of Montferrat negotiated with Venice, to transport 33,500 crusaders. This agreement required a full year of preparation on the part of the Venetians to build ships and train the sailors who would man them. What came back on the ships afterwards?