Aspremont-Lynden Castle, on the site of a mediaeval predecessor, was constructed by the noble family of d'Aspremont Lynden, Counts of Rekem, in the early 17th century, in the style of the Maasland Renaissance. The building served during the 19th and 20th centuries as a prison and a psychiatric hospital.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.