The power of the Venetian Republic depended on the Arsenale for 700 years. Built in the early 12C, at the height of the crusades, the huge complex is encircled by walls worthy of a fortress. Its size (15% of the city's surface) and rich history (first example of mass-production of vessels in history) make the site remarkable. While it cannot be visited, the Arsenale has two main entrances: one sea-facing, the other land bound, on the campo, marked by an imposing Renaissance portal.