One example could be 'The Crown', which is based on the true story of the British monarchy, which can be seen as a form of imperium in a way. It shows the power, the traditions, and the political influence of the royal family over the years.
Another example might be historical documentaries about the Ottoman Empire. These often tell the true story of how the Ottoman Imperium grew, its military conquests, its cultural achievements like architecture and art, and its complex system of governance. They are based on historical research and real events, giving a detailed look at what the Ottoman Imperium was really like.