Kalsmunt Castle (Burg) overlooks the town of Wetzlar in Hessen. It was an imperial castle which took its current form in the 12th century. The building passed through many hands over the years, originally with a military significance until around 1500 when it became a home to the Nassau-Weilburg family. It became ruinous from the 1600s, although attempts were made to restore it. The castle became property of the town of Wetzlar in 1803, and today it remains ruinous yet accessible to the public. The size of the building is impressive.