Visitors are seen at the State Hall of the Austrian National Library in Vienna, Austria, April 18, 2019. The State Hall of the Austrian National Library in Vienna is one of the most beautiful ancient libraries in the world. The State Hall, officially completed in 1730, is a treasure of Baroque architecture, with beautiful murals throughout the hall and 200,000 books spanning from the year 1501 to 1850. (Xinhua/Guo Chen)