Kalø Castle was founded in 1313 by the Danish king Erik Menved in order to establish a stronghold in northern Jutland to counter the ongoing rebellions by the local nobility and peasants against the crown. The castle was successful and from the 15th century and onwards the castle had a more peaceful role as the local administrative center. King Christian II held the future Swedish king Gustav Vasa captive at Kalø during 1518-1519, until he escaped.
When king Frederick III converted the elective monarchy into an absolute monarchy by the revolution of 1660 in Denmark, the castle lost its function. In 1661, Frederick III gave Kalø to Ulrik Frederik Gyldenløve, who in the following year (1662), tore down the now abandoned castle. The material was used to build his private palace in Copenhagen, now called the Charlottenborg Palace. Today the castle ruin is owned by the Danish State.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.