It is surrounded by medieval walls with towers and bastions, and has thirteen suburbs, one lying on an island in the river.
The knights strengthened Valletta and its harbour by bastions, curtain-walls, lines and forts, towards the sea, towards the land and on every available point, taking advantage in every particular of the natural rock and of the marvellous advantages of situation, rendering it then almost impregnable.
Thus, there may be a platform round the nuraghe, generally with two, three or four bastions, each often containing a chamber; or the main nuraghe may have additional chambers added to it.
The old ramparts and bastions (excluding the circuit of the citadel of 1591, now in great part demolished, in the south-east) make an enceinte of about 41 m., but the enclosed area is not all occupied by streets and houses.
One of the most ancient towns in Thuringia, Saalfeld, once the capital of the extinct duchy of Saxe-Saalfeld, is still partly surrounded by old walls and bastions, and contains some interesting medieval buildings, among them being a palace,, built in 1679 on the site of the Benedictine abbey of St Peter, which was destroyed during the Peasants' War.