Fredrikstad fortress was constructed between 1663-1666 by the officer Willem Coucheron and his son Anthony Coucheron following the order of the Dano-Norwegian King Frederick II. A temporary fortification had previously been built on the site during the Torstenson War (1644-1645) between Sweden and Denmark-Norway.
The first commander was appointed 6 January 1662; he was Lieutenant Colonel Johan Eberhard Speckhan. Besides the fortress the prison works was also under the supervision of the commander of Fredrikstad fortress. In 1716 the fortress was used by the naval hero Peder Tordenskjold when he attacked the Swedish fleet during the Battle of Dynekilen.
The only time the fortress were attacked was during the Swedish-Norwegian War (1814). The fortress, under the command of Nils Christian Frederik Hals, capitulated on 4 August 1814. The fortress was closed in 1903, but continued to serve as a garrison. Fredrikstad fortress is unique in Norway by being the only fortress that is preserved as it was. The remaining military installations in Fredrikstad were closed in 2002 and today the fortress with its mix of old buildings and art exhibitions is very popular for visitors.
The fortifications in Fredrikstad include Kongsten fort, Isegran fort, Cicignon fort, Huth fort, Akerøya fort and Slevik battery.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.