Jena or Jena is a German city in the province of Thuringia, and is considered the second largest city in it. The city is characterized by a mountainous nature with a number of valleys and rivers, and its most famous landmarks are the Optical Museum and the Saal River in addition to the Botanical Gardens, and a variety of museums. The city is famous for being the headquarters of the optics industry and centers of Scientific research, as it is one of the leading German cities in this field in the world. It also includes the University of Jena, which is one of the oldest universities in Germany, which was founded in 1558 AD.