The Bourtzi is the small fortress on the islet just off Nafplio's harbour, built by the Venetians in 1473 to guard the chain that closed the port. Its squat octagonal tower and curtain wall float on what looks at a distance like nothing more than a slab of rock.
You cannot walk to it — boats run from the quay in the old town in summer, a ten-minute ride. Off-season the islet often closes to visitors, but the view of it from the waterfront cafes is the iconic Nafplio postcard. Catch it at dusk with the lights of the town reflected behind.