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.
Angelokastro is a Byzantine castle on the island of Corfu. It is located at the top of the highest peak of the island"s shoreline in the northwest coast near Palaiokastritsa and built on particularly precipitous and rocky terrain. It stands 305 m on a steep cliff above the sea and surveys the City of Corfu and the mountains of mainland Greece to the southeast and a wide area of Corfu toward the northeast and northwest.
Angelokastro is one of the most important fortified complexes of Corfu. It was an acropolis which surveyed the region all the way to the southern Adriatic and presented a formidable strategic vantage point to the occupant of the castle.
Angelokastro formed a defensive triangle with the castles of Gardiki and Kassiopi, which covered Corfu"s defences to the south, northwest and northeast.
The castle never fell, despite frequent sieges and attempts at conquering it through the centuries, and played a decisive role in defending the island against pirate incursions and during three sieges of Corfu by the Ottomans, significantly contributing to their defeat.
During invasions it helped shelter the local peasant population. The villagers also fought against the invaders playing an active role in the defence of the castle.
The exact period of the building of the castle is not known, but it has often been attributed to the reigns of Michael I Komnenos and his son Michael II Komnenos. The first documentary evidence for the fortress dates to 1272, when Giordano di San Felice took possession of it for Charles of Anjou, who had seized Corfu from Manfred, King of Sicily in 1267.
From 1387 to the end of the 16th century, Angelokastro was the official capital of Corfu and the seat of the Provveditore Generale del Levante, governor of the Ionian islands and commander of the Venetian fleet, which was stationed in Corfu.
The governor of the castle (the castellan) was normally appointed by the City council of Corfu and was chosen amongst the noblemen of the island.
Angelokastro is considered one of the most imposing architectural remains in the Ionian Islands.