Is Isola della Piselli a real island?

Isola della Piselli, and the anatomatoria buried beneath it, are fictional. The subtle linguistic distinction between bìsi (with an accent, meaning peas) and bisi (without the accent, meaning snakes) is accurate, and both terms are specific to the Venetian dialect—neither of them would mean anything to a non-Venetian Italian, who understands peas to be piselli and snakes to be serpenti.

Poveglia is real, as is Isola di San Giorgio in Alga, including its history as a former lazaretto and lunatic asylum run by a sadistic physician who committed suicide by flinging himself from the tower. The Napoleonic ottagoni also exist, although none are named Ottagono Barberoni.

The reference to the papal bull De Sepulturis, issued by Boniface VIII in 1299 to prevent atrocities of the type that occurred in the anatomatoria, is historically accurate.