In Assassin's Creed II, the Basilica of San Marco is located in Venice.
The game recreates Venice as one of its major Renaissance settings, using canals, bridges, plazas, and prominent landmarks as navigational spaces. The Basilica of San Marco, known in Italian as Basilica di San Marco, is one of the city's most recognizable buildings and appears among the architectural landmarks explored by Ezio Auditore.
Florence is another major city in Assassin's Creed II and is the setting for much of the early story, so it is a common wrong answer. Rome becomes especially important in Assassin's Creed Brotherhood, while Milan is not the principal city associated with the game's landmark missions. The real Basilica of San Marco stands beside Piazza San Marco in Venice and is famous for its Byzantine-influenced architecture and mosaics. The game's version compresses geography for playability while retaining the city's historical identity.