The Bourtzi is the small Venetian water-castle on its own rocky islet in the middle of Nafplio's harbour, about 450 metres offshore. The Venetians built it in 1473 to defend the harbour entrance, stretching a chain across to the Akronafplia headland to seal off ships at night. For most of the Ottoman period it housed the garrison's Turkish governor.
Tour boats from the waterfront promenade run regularly across to the islet in summer, and you can climb the central tower for a perfect framed view back across to the old town and Palamidi. The crossing takes ten minutes; the visit itself thirty. Sunset from the boat or from the islet is the photo most visitors come for.