World Book Day, celebrated on 23 April by UNESCO, marks the anniversaries of the deaths of William Shakespeare and the author Miguel de Cervantes. First observed in 1995, the date has been marked as a celebration of books and the cultural wealth reading provides. In celebration of the day, here are some of the most beautiful libraries in the world, both modern and ancient, from a tiny library covered in firewood to an all-white building inspired by the Pantheon of ancient Rome.