The Wilhelmsturm located on a hill above the town, nowadays is Dillenburg’s main landmark. The tower was built between 1872 and 1875 on the former upper courtyard of Dillenburg Castle. That medieval castle was erected in 1130, but destroyed during the Seven Years War in 1760. The castle was the family ancestral seat of the House of Nassau.

The Wilhelmsturm is 41 meters high and overlooks the town of Dillenburg. The tower was constructed as a permanent memorial of Willem van Oranje (William of Ornage or William the Silent) who was born in the castle. Nowadays it houses the Orange-Nassau Museum.

Willem van Oranje was the leader of the Dutch revolt against the Spanish occupation during the Eighty Years’ War (1568 -1648), which resulted in the formal independence of the Dutch Republic. Next to the tower stands a monument in honour of Dillenburgs greatest son. This statue of William of Orange was erected to mark the 125th anniversary of the Wilhelmsturm and unveiled in the year 2000 by Queen Beatrix of the Netherlands.