The medieval part of the town of Kotor is located on a triangular piece of land that is bordered by the most inner extension of the Bay of Kotor at its south-western side, the river Skurda toward the North, and the mountain of St. John (San Giovanni) towards the East. City walls protect the city on its northern and south-western side, towards the waters. The walls are fortified by bastions, most prominent being the Kampana tower and citadel (13th to 14th century) near the point where the river enters the bay. Close to it is the Sea Gate (also Main Gate) from 1555 allowing access from the bay, the two other gates to the city are the River Gate (also North Gate) from 1540 with the nearby Bembo Bastion from 1540 and the Gurdic Gate (also South Gate), the latter modified many times and fortified by the Gurdic Bastion from 1470. The Bembo Bastion has been converted into an open theatre. Two additional gates were present, one walled up south of the Sea Gate, the other, Spiljarskia Gate, within the ramparts of the hillside towards the old road to Cetinje. From the Bembo Bastion and the Gurdic Bastion ramparts climb up to the top of the St. John Mountain that backs the city. The ramparts have positions at various points; within them is a network of communications as well as additional buildings including the Church of Our Lady of Remedy from 1518. On top of the mountain is the San Giovanni castel at a 280-meter height dominating the eastern bay, the fortification system and the city. Behind the castle hill the inhabitable and mountainous countryside further ascends toward the Lovcen. The circumference of the outer wall is 4.5 km, with a thickness between 2 and 16 m, and a height up to 20 m.