Nanstein Castle was built around the year 1162 after Holy Roman Emperor Frederick I demanded its construction as additional defense for the Palatinate.
In 1504, German knight Franz von Sickingen, inherited part of the castle after his father's death in the War of the Bavarian Succession, finally acquiring the entire castle in 1518. He immediately began extensive refortification to make the castle suitable for firearms.
Nanstein is well known for an elaborate siege during the Knights' Revolt in 1523 which claimed the life of von Sickingen. The fall of Nanstein was a symbol for the decline of castles in the Palatinate.
In 1542, von Sickingen's sons recovered Nanstein as a fief and started reconstruction of the castle. Reinhard von Sickingen completed the reconstruction in 1595. In 1668, Elector Charles I Louis forced Lotharingian troops from the castle and razed the fortifications.
In the 19th century the first conservation work was done on Nanstein, and this has continued to the present day.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.