Wetzlar is also the cradle of 35 mm photography. It was Oskar Barnack who had the ingenious idea of creating the 35 mm format for his legendary Leica, which entered series production in 1925. The "Viseum Wetzlar" builds on this tradition. Visitors can gain fascinating insights into the world of technology here. A large number of exhibits on the topics of optics and fine mechanics are presented in a historic building in the heart of the old town. But visitors are not limited to looking; researching and experimenting for themselves is the key. Visitors and tourists also have the opportunity to discover the optics trail, with its 24 stations and phenomena on the topic of optics. The audio guide is perfect for this, providing a unique and entertaining tour of the optics trail. Located in the heart of the Lahn Valley, the town is also an outstanding starting point for cycling tours on the Lahn Valley cycle path or for canoeing trips on the Lahn river.