- Jena is a city in the state of Thuringia, in central Germany. It is located about 40 kilometers west of Erfurt and has a population of approximately 111,000 people. Jena is known for its rich history and is home to several important educational and research institutions, including the Friedrich Schiller University and the Max Planck Institute for Biogeochemistry. The city is also famous for its optical industry, with companies such as Carl Zeiss and Jenoptik having a strong presence in the region. Jena is surrounded by beautiful natural landscapes, including the Saale River and the Thuringian Forest, making it a popular destination for outdoor activities such as hiking and cycling. The city offers a vibrant cultural scene, with numerous theaters, museums, and music festivals taking place throughout the year.