Almarestäkets castle was built in the 1100s to protect the Sigtuna and Uppsala cities. It was also called as St. Erik's castle after Eric IX. Throughout the Middle Ages there was a struggle between the Crown and Church who can control the castle.
The castle was first mentioned in the late 1300s. In 1440 got Archbishop Nicolaus Ragvaldi permission to build a new castle, which was completed about ten years later. In the 1510s troubles Almarestäkets was in possession of Bishop Gustav Trolle between 1516-17. The castle was sieged by his main enemy Sten Sture the Younger in 1517. Archbishop Gustav Trolle locked himself in there to avoid trial, and the Swedish government demanded and carried out the demolition of the fortress. The procedure was formally unauthorized because at the time State property was to be separate from Church property. As a revenge for this and other perceived injustices, Trolle, assisted by the Danish King Christian II, took revenge in the Stockholm Bloodbath of 1520.
Today there are visible traces of castle foundations with potholes filled with stone and occasional bricks.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.