At the entrance of the harbour of Nafplio, from the 15th century, has stood the fortress called the "Bourtzi". It is one of the most important parts of the fortification-system of the historic city. The fort is laid out to fit the shape of the island, standing directly on its bedrock. The ground plan is elongated, with the main axis oriented east-west. At its ends it is shaped by bastions of curved shape. On the long sides are towers with gates, protected by barbicans, semicircular on the north side and square to the south. On either side of the southern barbican are gun emplacements, polygonal in plan.
A large part of the fortress is occupied by the massive central tower. It has a six-sided ground plan. Inside there are three superimposed vaulted spaces and also a vaulted water-cistern on a lower level. Access to them was only possible from the roof. Within the thickness of the wall and in communication with the penultimate level is another room, perhaps for storing the gunpowder.
In its initial phase the fortress had numerous battlements of the ‘dovetail’ type. However, from early on concerns were expressed about aspects of its design: for example the great height of the tower left it exposed to the increasingly heavy impact of artillery fire. Accordingly, many of the battlements, both on the tower and the walls, were gradually transformed into strong parapets. These conversions can be found on the elevated ramparts of the northern barbican and the north wall, on the revamped parapet on the south side, in order to more effectively protect the entrance of the harbour with cannons, and in the construction of the parapet with the cloisonne system of construction in the eastern bastion and the erection of buildings of less importance inside. The stairway leading to the entrance of the central tower, which was originally accessible by a drawbridge, is also the result of later intervention.
