It started with a castle on the Zenne island in the 10th century and already had a fortified wall in 1100. This protection was transformed into a commercial place on the important trade route from Cologne to Bruges. The second city wall in the 14th century already surrounded the upper and lower city, the upper city being the home of the rich merchants, while the lower part developed in the 18th and 19th centuries as a newly formed political center. Brussels became the capital of the Burgundian Netherlands. In the 15th century Brussels experienced a great intellectual prosperity and played the main role in the struggle of the revolting Netherlands against the Spanish army. In 1695 it was destroyed by the Spanish troops; in 1794 Brussels became the capital of the French department Dyle and in 1815 after the defeat of Napoleon at Waterloo the second capital of the United Kingdom of the Netherlands. In 1830 the revolution started which led to the independence of Belgium.