The Arsenale di Venezia is Venice's colossal medieval shipyard, once the largest industrial complex in Europe and now the primary venue for the Venice Biennale art and architecture exhibitions. This vast complex in the Castello sestiere is where the Venetian Republic built warships and merchant galleys on an almost industrial scale, centuries before the Industrial Revolution. At its peak in the 16th century, the Arsenale employed up to 16,000 workers (known as arsenalotti) and could reportedly assemble a fully equipped galley in a single day using an early form of assembly-line production. The complex covers roughly 32 hectares, about 15 percent of Venice's total land area, enclosed by crenellated brick walls and accessible through a monumental Renaissance gateway flanked by marble lions (one of them looted from Piraeus in 1687). For centuries, the Arsenale was a restricted military zone, and much of it remained closed to the public until relatively recently. Today, large sections serve as the primary venue for the Venice Biennale, hosting the International Art Exhibition and the International Architecture Exhibition in alternating years. During Biennale periods (typically May through November), the vast Corderie (ropemaking halls) and Artiglierie (artillery sheds) are transformed into exhibition spaces. Outside Biennale season, access is more limited, though the impressive gateway, the towers, and the surrounding waterfront can be appreciated from the outside. The Naval History Museum, located a short walk south of the main entrance, displays ship models, maritime instruments, and artifacts from the Republic's seafaring centuries, including a model of the last Bucintoro, the ceremonial barge of the Doge.