Venice’s first arsenal was already in existence by 1104 when the Crusades meant huge demand for shipbuilding. Surrrounded by towered walls and canals, the Arsenale has two main entrances, both oriented towards the rio (canal) of the same name. In this military zone (closed to visitors), the water entrance is marked by twin towers built in 1686. The land entrance, giving onto the square, has an imposing Renaissance gate adorned with lions.