there are loads to compare and contrast in this broad question : the influences of the different languages and other linguistic influences; political systems and structure ; design and organisation of travel and water transportation ; architectural style; social structure and the organisation of labour; military ambitions and how these were accomplished or failed; the emphasis on culture, philosophy, mathematics, science. These are but a few example, I am sure there are other ideas and information to explore in your notes,books and library. I hope your essay goes well, You may have to focus on certain aspects to give some depth and detail to your assignment