The map symbols for Templar Lairs are actually that of the Knights Hospitallier.
Ezio Auditore da Firenze loosely translates to "like an eagle, auditor of/from Firenze". Auditor derives from the family profession in banking; Firenze is the Italian version of Florence, Ezio's birthplace.
The cars in Abstergo's underground parking lot are from the video game Driver: Parallel Lines (2006).
When you first meet Ezio's uncle, Mario, he says, "It's a me, Mario!", a reference to Super Mario Bros.
This marks the sixth of seven games that Jesper Kyd has made music for in which the main protagonist is an assassin. The first four being the Hitman series and the last three being the Assassin's Creed series.