Fürstliches Residenzschloß, in the center of the Detmold town park, is a fine example of Weser Renaissance style. In 1263, Bernard III of Lippe fortified the settlement at the crossing of the trade route from Paderborn to Lemgo over the Werre River with stone walls and granted it a municipal charter. In 1550, Detmold became the permanent residence of Count Simon III of Lippe. The counts were elevated to princes in 1789, and Detmold remained the capital of the small Principality of Lippe until the end of the World War I in 1918, when all princely states in Germany were abolished. Detmold Castle is still in the hands of the Princes of Lippe.
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.