Novgorod Kremlin (Detinets) stands on the left bank of the Volkhov River. It is part of the UNESCO World Heritage Site of Historic Monuments of Novgorod and Surroundings. The compound was originally the site of a pagan burial ground upon which the first bishop of Novgorod, Ioakim Korsunianin built the Cathedral of Holy Wisdom upon his arrival in the area in 989 or so. Thus the compound was and remained largely an ecclesiastical site, although many Novgorodian boyars built their houses in the southern part of the Detinets.
The first reference to fortifications on the site dates to 1044, with additional construction taking place in 1116. These were probably earthen embankments topped by a wooden palisade, although stone towers and walls were built in 1302. Archbishop Vasily Kalika (1330–1352) rebuilt the stone wall along the eastern side of the Detinets in 1331-1335. The rest was completed in stone only in 1400. Part of Vasily"s walls collapsed into the Volkhov River in 1437 and were rebuilt by Archbishop Evfimy II (1429–1458).
The current fortress was built between 1484 and 1490 by Muscovite builders in the wake of Grand Prince Ivan III"s conquest of the city in 1478; a third of it was paid for by the Novgorodian archbishop Gennady, a Muscovite appointee (1484–1504). It is a large oval 545 meters long and 240 meter wide with nine surviving towers (three additional towers have not survived). The tallest tower, the Kokui tower is capped by a silver dome. It was built in the eighteenth century and its name is of Swedish origin. Today it is possible to enter this tower and climb to the top. The walls are 1,487 meters in circumference.References:
The city walls of Avila were built in the 11th century to protect the citizens from the Moors. They have been well maintained throughout the centuries and are now a major tourist attraction as well as a UNESCO World Heritage Site. Visitors can walk around about half of the length of the walls.
The layout of the city is an even quadrilateral with a perimeter of 2,516 m. Its walls, which consist in part of stones already used in earlier constructions, have an average thickness of 3 m. Access to the city is afforded by nine gates of different periods; twin 20 m high towers, linked by a semi-circular arch, flank the oldest ones, Puerta de San Vicente and Puerta del Alcázar.