Visible from the street, the impressive Renaissance gateway, the Porta Magna (1460), was the first classical structure to be built in Venice. It is guarded by four lions—war booty of Francesco Morosini, who took the Peloponnese from the Turks in 1687. The 10-foot-tall lion on the left stood sentinel more than 2,000 years ago near Athens, and experts say its mysterious inscription is runic "graffiti" left by Viking mercenaries hired to suppress 11th-century revolts in Piraeus. If you look at the winged lion above the doorway, you'll notice that the Gospel at his paws is open, but lacks the customary Pax inscription; praying for peace perhaps seemed inappropriate above a factory that manufactured weapons. The interior is not regularly open to the public, since it belongs to the Italian Navy, but it opens for the Biennale and for Venice's festival of traditional boats, Mare Maggio (www.maremaggio.it), held every May. If you're here during those times, don't miss the chance for a look inside; you can enter from the back via a northern-side walkway leading from the Ospedale vaporetto stop.
The Arsenale is said to have been founded in 1104 on twin islands. The immense facility that evolved—it was the largest industrial complex in Europe built prior to the Industrial Revolution—was given the old Venetian dialect name arzanà, borrowed from the Arabic darsina'a, meaning "workshop." At the height of its activity, in the early 16th century, it employed as many as 16,000 arsenalotti, workers who were among the most respected shipbuilders in the world. The Arsenale developed a type of pre-Industrial Revolution assembly line, which allowed it to build ships with astounding speed and efficiency. (This innovation existed even in Dante's time, and he immortalized these toiling workers armed with boiling tar in his Inferno, Canto 21.) The Arsenale's efficiency was confirmed time and again—whether building 100 ships in 60 days to battle the Turks in Cyprus (1597) or completing one perfectly armed warship, start to finish, while King Henry III of France attended a banquet.
Campo dell'Arsenale, Venice, 30135, Italy